HotFreeBooks.com
The World's Greatest Books - Volume 15 - Science
Author: Various
Previous Part     1  2  3  4  5  6  7     Next Part
Home - Random Browse

Most entomologists have observed with what ingenuity and sureness dragon-flies distinguish, follow, and catch the smallest insects on the wing. Of all insects, they have the best sight. Their enormous convex eyes have the greatest number of facets. Their number has been estimated at 12,000, and even at 17,000. Their aerial chases resemble those of the swallows. By trying to catch them at the edge of a large pond, one can easily convince oneself that the dragon-flies amuse themselves by making sport of the hunter; they will always allow one to approach just near enough to miss catching them. It can be seen to what degree they are able to measure the distance and reach of their enemy.

It is an absolute fact that dragon-flies, unless it is cold or in the evening, always manage to fly at just that distance at which the student cannot touch them; and they see perfectly well whether one is armed with a net or has nothing but his hands; one might even say that they measure the length of the handle of the net, for the possession of a long handle is no advantage. They fly just out of reach of one's instrument, whatever trouble one may give oneself by hiding it from them and suddenly lunging as they fly off. Whoever watches butterflies and flies will soon see that these insects also can measure the distance of such objects as are not far from them. The males and females of bees and ants distinguish one another on the wing. It is rare for an individual to lose sight of the swarm or to miss what it pursues flying. It has been proved that the sense of smell has nothing to do with this matter. Thus insects, though without any power of accommodation for light or distance, are able to perceive objects at different distances.

It is known that many insects will blindly fly and dash against a lamp at night, until they burn themselves. It has often been wrongly thought that they are fascinated. We ought first to remember that natural lights, concentrated at one point like our artificial lights, are extremely rare in Nature. The light of day, which is the light of wild animals, is not concentrated at one point. Insects, when they are in darkness—underground, beneath bark or leaves—are accustomed to reach the open air, where the light is everywhere diffused, by directing themselves towards the luminous point. At night, when they fly towards a lamp, they are evidently deceived, and their small brains cannot comprehend the novelty of this light concentrated at one spot. Consequently, their fruitless efforts are again and again renewed against the flame, and the poor innocents end by burning themselves. Several domestic insects, which have become little by little adapted to artificial light in the course of generations, no longer allow themselves to be deceived thereby. This is the case with house-flies.

Bees distinguish all colours, and seldom confound any but blue and green; while wasps scarcely react to differences of colour, but note better the shape of an object, and note, for instance, where the place of honey is; so that a change of colour on the disc whereon the honey is placed hardly upsets them. Further, wasps have a better sense of smell than bees.

The chief discovery regarding the vision of insects made in the last thirty years is that of Lubbock, who proved that ants perceive the ultra-violet rays of the spectrum, which we are unable, or almost unable, to perceive.

It has lately been proved also that many insects appreciate light by the skin.

They do not see as clearly as we do; but when they possess well-developed compound eyes they appreciate size, and more or less distinctly the contours of objects.

Ants have a great faculty for recognition, which probably testifies to their vision and visual memory. Lubbock observed ants which actually recognised each other after more than a year of separation.

III.—Smell, Taste, Hearing, Pain

Smell is very important in insects. It is difficult for us to judge of, since man is of all the vertebrates except the whales, perhaps, the one in which this sense is most rudimentary. We can evidently, therefore, form only a feeble idea of the world of knowledge imparted by a smell to a dog, a mole, a hedgehog, or an insect. The instruments of smell are the antennae. A poor ant without antennae is as lost as a blind man who is also deaf and dumb. This appears from its complete social inactivity, its isolation, its incapacity to guide itself and to find its food. It can, therefore, be boldly supposed that the antennae and their power of smell, as much on contact as at a distance, constitute the social sense of ants, the sense which allows them to recognise one another, to tend to their larvae, and mutually help one another, and also the sense which awakens their greedy appetites, their violent hatred for every being foreign to the colony, the sense which principally guides them—a little helped by vision, especially in certain species—in the long and patient travels which they have to undertake, which makes them find their way back, find their plant-lice, and all their other means of subsistence.

As the philosopher Herbert Spencer has well pointed out, the visceral sensations of man, and those internal senses which, like smell, can only make an impression of one kind as regards space—two simultaneous odours can only be appreciated by us as a mixture—are precisely those by which we can gain little or no information relative to space. Our vision, on the contrary, which localises the rays from various distant points of space on various distinct points of our retina at the same time, is our most relational sense, that which gives us the most vast ideas of space.

But the antennae of insects are an olfactory organ turned inside out, prominent in space, and, further, very mobile. This allows us to suppose that the sense of smell may be much more relational than ours, that the sensations thence derived give them ideas of space and of direction which may be qualitatively different from ours.

Taste exists in insects, and has been very widely written on, but somewhat inconclusively. The organs of taste probably are to be found in the jaws and at the base of the tongue. This sense can be observed in ants, bees, and wasps; and everyone has seen how caterpillars especially recognise by taste the plants which suit them.

Much has been written on the hearing of insects; but, in my judgment, only crickets and several other insects of that class appear to perceive sounds. Erroneous views have been due to confusing hearing with mechanical vibrations.

We must not forget that the specialisation of the organ of hearing has reached in man a delicacy of detail which is evidently not found again in lower vertebrates.

Pain is much less developed in insects than in warm-blooded vertebrates. Otherwise, one could not see either an ant, with its abdomen or antennae cut off, gorge itself with honey; or a humble-bee, in which the antennae and all the front of the head had been removed, go to find and pillage flowers; or a spider, the foot of which had been broken, feed immediately on this, its own foot, as I myself have seen; or, finally, a caterpillar, wounded at the "tail" end, devour itself, beginning behind, as I have observed more than once.

IV.—Insect Reason and Passions

Insects reason, and the most intelligent among them, the social hymenoptera, especially the wasps and ants, even reason much more than one is tempted to believe when one observes the regularly recurring mechanism of their instincts. To observe and understand these reasonings well, it is necessary to mislead their instinct. Further, one may remark little bursts of plastic judgment, of combinations—extremely limited, it is true—which, in forcing them an instant from the beaten track of their automatism, help them to overcome difficulties, and to decide between two dangers. From the point of view of instinct and intelligence, or rather of reason, there are not, therefore, absolute contrasts between the insect, the mammal, and the man.

Finally, insects have passions which are more or less bound up with their instincts. And these passions vary enormously, according to the species. I have noted the following passions or traits of character among ants: choler, hatred, devotion, activity, perseverance, and gluttony. I have added thereto the discouragement which is sometimes shown in a striking manner at the time of a defeat, and which can become real despair; the fear which is shown among ants when they are alone, while it disappears when they are numerous. I can add further the momentary temerity whereby certain ants, knowing the enemy to be weakened and discouraged, hurl themselves alone in the midst of the black masses of enemies larger than themselves, hustling them without taking the least further precaution.

When we study the manners of an insect, it is necessary for us to take account of its mental faculties as well as of its sense organs. Intelligent insects make better use of their senses, especially by combining them in various ways. It is possible to study such insects in their homes in a more varied and more complete manner, allowing greater accuracy of observations.



GALILEO

Dialogues on the System of the World

Galileo Galilei, famous as an astronomer and as an experimental physicist, was born at Pisa, in Italy, Feb. 18, 1564. His talents were most multifarious and remarkable; but his mathematical and mechanical genius was dominant from the first. As a child he constructed mechanical toys, and as a young man he made one of his most important discoveries, which was that of the pendulum as an agent in the measurement of time, and invented the hydrostatic balance, by which the specific gravity of solid bodies might be ascertained. At the age of 24 a learned treatise on the centre of gravity of solids led to a lectureship at Pisa University. Driven from Pisa by the enmity of Aristotelians, he went to Padua University, where he invented a kind of thermometer, a proportional compass, a microscope, and a telescope. The last invention bore fruit in astronomical discoveries, and in 1610 he discovered four of the moons of Jupiter. His promulgation of the Copernican doctrine led to renewed attacks by the Aristotelians, and to censure by the Inquisition. (See Religion, vol. xiii.) Notwithstanding this censure, he published in 1632 his "Dialogues on the System of the World." The interlocutors in the "Dialogues," with the exception of Salviatus, who expounds the views of the author himself, represent two of Galileo's early friends. For the "Dialogues" he was sentenced by the Inquisition to incarceration at its pleasure, and enjoined to recite penitential psalms once a week for three years. His life thereafter was full of sorrow, and in 1637 blindness added to his woes; but the fire of his genius still burnt on till his death on January 8, 1642.

Does the Earth Move

SALVIATUS: Now, let Simplicius propound those doubts which dissuade him from believing that the earth may move, as the other planets, round a fixed centre.

SIMPLICIUS: The first and greatest difficulty is that it is impossible both to be in a centre and to be far from it. If the earth move in a circle it cannot remain in the centre of the zodiac; but Aristotle, Ptolemy and others have proved that it is in the centre of the zodiac.

SALVIATUS: There is no question that the earth cannot be in the centre of a circle round whose circumference it moves. But tell me what centre do you mean?

SIMPLICIUS: I mean the centre of the universe, of the whole world, of the starry sphere.

SALVIATUS: No one has ever proved that the universe is finite and figurative; but granting that it is finite and spherical, and has therefore a centre, we have still to give reasons why we should believe that the earth is at its centre.

SIMPLICIUS: Aristotle has proved in a hundred ways that the universe is finite and spherical.

SALVIATUS: Aristotle's proof that the universe was finite and spherical was derived essentially from the consideration that it moved; and seeing that centre and figure were inferred by Aristotle from its mobility, it will be reasonable if we endeavour to find from the circular motions of mundane bodies the centre's proper place. Aristotle himself came to the conclusion that all the celestial spheres revolve round the earth, which is placed at the centre of the universe. But tell me, Simplicius, supposing Aristotle found that one of the two propositions must be false, and that either the celestial spheres do not revolve or that the earth is not the centre round which they revolve, which proposition would he prefer to give up?

SIMPLICIUS: I believe that the Peripatetics——

SALVIATUS: I do not ask the Peripatetics, I ask Aristotle. As for the Peripatetics, they, as humble vassals of Aristotle, would deny all the experiments and all the observations in the world; nay, would also refuse to see them, and would say that the universe is as Aristotle writeth, and not as Nature will have it; for, deprived of the shield of his authority, with what do you think they would appear in the field? Tell me, therefore, what Aristotle himself would do.

SIMPLICIUS: To tell you the truth, I do not know how to decide which is the lesser inconvenience.

SALVIATUS: Seeing you do not know, let us examine which would be the more rational choice, and let us assume that Aristotle would have chosen so. Granting with Aristotle that the universe has a spherical figure and moveth circularly round a centre, it is reasonable to believe that the starry orbs move round the centre of the universe or round some separate centre?

SIMPLICIUS: I would say that it were much more reasonable to believe that they move with the universe round the centre of the universe.

SALVIATUS: But they move round the sun and not round the earth; therefore the sun and not the earth is the centre of the universe.

SIMPLICIUS: Whence, then, do you argue that it is the sun and not the earth that is the centre of the planetary revolutions?

SALVIATUS: I infer that the earth is not the centre of the planetary revolutions because the planets are at different times at very different distances from the earth. For instance, Venus, when it is farthest off, is six times more remote from us than when it is nearest, and Mars rises almost eight times as high at one time as at another.

SIMPLICIUS: And what are the signs that the planets revolve round the sun as centre?

SALVIATUS: We find that the three superior planets—Mars, Jupiter, and Saturn—are always nearest to the earth when they are in opposition to the sun, and always farthest off when they are in conjunction; and so great is this approximation and recession that Mars, when near, appears very nearly sixty times greater than when remote. Venus and Mercury also certainly revolve round the sun, since they never move far from it, and appear now above and now below it.

SAGREDUS: I expect that more wonderful things depend on the annual revolution than upon the diurnal rotation of the earth.

SALVIATUS: YOU do not err therein. The effect of the diurnal rotation of the earth is to make the universe seem to rotate in the opposite direction; but the annual motion complicates the particular motions of all the planets. But to return to my proposition. I affirm that the centre of the celestial convolutions of the five planets—Saturn, Jupiter, Mars, Venus, and Mercury, and likewise of the earth—is the sun.

As for the moon, it goes round the earth, and yet does not cease to go round the sun with the earth. It being true, then, that the five planets do move about the sun as a centre, rest seems with so much more reason to belong to the said sun than to the earth, inasmuch as in a movable sphere it is more reasonable that the centre stand still than any place remote from the centre.

To the earth, therefore, may a yearly revolution be assigned, leaving the sun at rest. And if that be so, it follows that the diurnal motion likewise belongs to the earth; for if the sun stood still and the earth did not rotate, the year would consist of six months of day and six months of night. You may consider, likewise, how, in conformity with this scheme, the precipitate motion of twenty-four hours is taken away from the universe; and how the fixed stars, which are so many suns, are made, like our sun, to enjoy perpetual rest.

SAGREDUS: The scheme is simple and satisfactory; but, tell me, how is it that Pythagoras and Copernicus, who first brought it forward, could make so few converts?

SALVIATUS: If you know what frivolous reasons serve to make the vulgar, contumacious and indisposed to hearken, you would not wonder at the paucity of converts. The number of thick skulls is infinite, and we need neither record their follies nor endeavour to interest them in subtle and sublime ideas. No demonstrations can enlighten stupid brains.

My wonder, Sagredus, is different from yours. You wonder that so few are believers in the Pythagorean hypothesis; I wonder that there are any to embrace it. Nor can I sufficiently admire the super-eminence of those men's wits that have received and held it to be true, and with the sprightliness of their judgments have offered such violence to their senses that they have been able to prefer that which their reason asserted to that which sensible experience manifested. I cannot find any bounds for my admiration how that reason was able, in Aristarchus and Copernicus, to commit such a rape upon their senses, as in despite thereof to make herself mistress of their credulity.

SAGREDUS: Will there still be strong opposition to the Copernican system?

SALVIATUS: Undoubtedly; for there are evident and sensible facts to oppose it, requiring a sense more sublime than the common and vulgar senses to assist reason.

SAGREDUS: Let us, then, join battle with those antagonistic facts.

SALVIATUS: I am ready. In the first place, Mars himself charges hotly against the truth of the Copernican system. According to the Copernican system, that planet should appear sixty times as large when at its nearest as when at its farthest; but this diversity of magnitude is not to be seen. The same difficulty is seen in the case of Venus. Further, if Venus be dark, and shine only with reflected light, like the moon, it should show lunar phases; but these do not appear.

Further, again, the moon prevents the whole order of the Copernican system by revolving round the earth instead of round the sun. And there are other serious and curious difficulties admitted by Copernicus himself. But even the three great difficulties I have named are not real. As a matter of fact, Mars and Venus do vary in magnitude as required by theory, and Venus does change its shape exactly like the moon.

SAGREDUS: But how came this to be concealed from Copernicus and revealed to you?



SIR FRANCIS GALTON

Essays in Eugenics

Sir Francis Galton, born at Birmingham, England, in 1822, was a grandson of Dr. Erasmus Darwin. He graduated from Trinity College, Cambridge, in 1844. Galton travelled in the north of Africa, on the White Nile and in the western portion of South Africa between 1844 and 1850. Like his immortal cousin, Charles Darwin, Sir Francis Galton is a striking instance of a man of great and splendid inheritance, who, also inheriting wealth, devotes it and his powers to the cause of humanity. He published several books on heredity, the first of which was "Hereditary Genius." The next "Inquiries into Human Faculty," which was followed by "Natural Inheritance." The "Essays in Eugenics" include all the most recent work of Sir Francis Galton since his return to the subject of eugenics in 1901. This volume has just been published by the Eugenics Education Society, of which Sir Francis Galton is the honorary president. As epitomised for this work, the "Essays" have been made to include a still later study by the author, which will be included in future editions of the book. The epitome has been prepared by special permission of the Eugenics Education Society, and those responsible hope that it will serve in some measure to neutralise the outrageous, gross, and often wilful misrepresentations of eugenics of which many popular writers are guilty.

I.—The Aims and Methods of Eugenics

The following essays help to show something of the progress of eugenics during the last few years, and to explain my own views upon its aims and methods, which often have been, and still sometimes are, absurdly misrepresented. The practice of eugenics has already obtained a considerable hold on popular estimation, and is steadily acquiring the status of a practical question, and not that of a mere vision in Utopia.

The power by which eugenic reform must chiefly be effected is that of public opinion, which is amply strong enough for that purpose whenever it shall be roused. Public opinion has done as much as this on many past occasions and in various countries, of which much evidence is given in the essay on restrictions in marriage. It is now ordering our acts more intimately than we are apt to suspect, because the dictates of public opinion become so thoroughly assimilated that they seem to be the original and individual to those who are guided by them. By comparing the current ideas at widely different epochs and under widely different civilisations, we are able to ascertain what part of our convictions is really innate and permanent, and what part has been acquired and is transient.

It is, above all things, needful for the successful progress of eugenics that its advocates should move discreetly and claim no more efficacy on its behalf than the future will justify; otherwise a reaction will be justified. A great deal of investigation is still needed to show the limit of practical eugenics, yet enough has been already determined to justify large efforts being made to instruct the public in an authoritative way, with the results hitherto obtained by sound reasoning, applied to the undoubted facts of social experience.

The word "eugenics" was coined and used by me in my book "Human Faculty," published as long ago as 1883. In it I emphasised the essential brotherhood of mankind, heredity being to my mind a very real thing; also the belief that we are born to act, and not to wait for help like able-bodied idlers, whining for doles. Individuals appear to me as finite detachments from an infinite ocean of being, temporarily endowed with executive powers. This is the only answer I can give to myself in reply to the perpetually recurring questions of "why? whence? and whither?" The immediate "whither?" does not seem wholly dark, as some little information may be gleaned concerning the direction in which Nature, so far as we know of it, is now moving—namely, towards the evolution of mind, body, and character in increasing energy and co-adaptation.

The ideas have long held my fancy that we men may be the chief, and perhaps the only executives on earth; that we are detached on active service with, it may be only illusory, powers of free-will. Also that we are in some way accountable for our success or failure to further certain obscure ends, to be guessed as best we can; that though our instructions are obscure they are sufficiently clear to justify our interference with the pitiless course of Nature whenever it seems possible to attain the goal towards which it moves by gentler and kindlier ways.

There are many questions which must be studied if we are to be guided aright towards the possible improvement of mankind under the existing conditions of law and sentiment. We must study human variety, and the distribution of qualities in a nation. We must compare the classification of a population according to social status with the classification which we would make purely in terms of natural quality. We must study with the utmost care the descent of qualities in a population, and the consequences of that marked tendency to marriage within the class which distinguishes all classes. Something is to be learnt from the results of examinations in universities and colleges.

It is desirable to study the degree of correspondence that may exist between promise in youth, as shown in examinations, and subsequent performance. Let me add that I think the neglect of this inquiry by the vast army of highly educated persons who are connected with the present huge system of competitive examination to be gross and unpardonable. Until this problem is solved we cannot possibly estimate the value of the present elaborate system of examinations.

II.—Restrictions in Marriage

It is necessary to meet an objection that has been repeatedly urged against the possible adoption of any system of eugenics, namely, that human nature would never brook interference with the freedom of marriage. But the question is how far have marriage restrictions proved effective when sanctified by the religion of the time, by custom, and by law. I appeal from armchair criticism to historical facts. It will be found that, with scant exceptions, marriage customs are based on social expediency and not on natural instincts. This we learn when we study the fact of monogamy, and the severe prohibition of polygamy, in many times and places, due not to any natural instinct against the practice, but to consideration of the social well-being. We find the same when we study endogamy, exogamy, Australian marriages, and the control of marriage by taboo.

The institution of marriage, as now sanctified by religion and safeguarded by law in the more highly civilised nations, may not be ideally perfect, nor may it be universally accepted in future times, but it is the best that has hitherto been devised for the parties primarily concerned, for their children, for home life, and for society. The degree of kinship within which marriage is prohibited is, with one exception, quite in accordance with modern sentiment, the exception being the disallowal of marriage with the sister of a deceased wife, the propriety of which is greatly disputed and need not be discussed here. The marriage of a brother and sister would excite a feeling of loathing among us that seems implanted by nature, but which, further inquiry will show, has mainly arisen from tradition and custom.

The evidence proves that there is no instinctive repugnance felt universally by man to marriage within the prohibited degrees, but that its present strength is mainly due to what I may call immaterial considerations. It is quite conceivable that a non-eugenic marriage should hereafter excite no less loathing than that of a brother and sister would do now.

The dictates of religion in respect to the opposite duties of leading celibate lives, and of continuing families, have been contradictory. In many nations it is and has been considered a disgrace to bear no children, and in other nations celibacy has been raised to the rank of a virtue of the highest order. During the fifty or so generations that have elapsed since the establishment of Christianity, the nunneries and monasteries, and the celibate lives of Catholic priests, have had vast social effects, how far for good and how far for evil need not be discussed here. The point I wish to enforce is the potency, not only of the religious sense in aiding or deterring marriage, but more especially the influence and authority of ministers of religion in enforcing celibacy. They have notoriously used it when aid has been invoked by members of the family on grounds that are not religious at all, but merely of family expediency. Thus at some times and in some Christian nations, every girl who did not marry while still young was practically compelled to enter a nunnery, from which escape was afterwards impossible.

It is easy to let the imagination run wild on the supposition of a whole-hearted acceptance of eugenics as a national religion; that is, of the thorough conviction by a nation that no worthier object exists for man than the improvement of his own race, and when efforts as great as those by which nunneries and monasteries were endowed and maintained should be directed to fulfil an opposite purpose. I will not enter further into this. Suffice it to say, that the history of conventual life affords abundant evidence on a very large scale of the power of religious authority in directing and withstanding the tendencies of human nature towards freedom in marriage.

Seven different forms of marriage restriction may be cited to show what is possible. They are monogamy, endogamy, exogamy, Australian marriages, taboo, prohibited degrees, and celibacy. It can be shown under each of these heads how powerful are the various combinations of immaterial motives upon marriage selection, how they may all become hallowed by religion, accepted as custom, and enforced by law. Persons who are born under their various rules live under them without any objection. They are unconscious of their restrictions, as we are unaware of the tension of the atmosphere. The subservience of civilised races to their several religious superstitions, customs, authority, and the rest, is frequently as abject as that of barbarians.

The same classes of motives that direct other races direct ours; so a knowledge of their customs helps us to realise the wide range of what we may ourselves hereafter adopt, for reasons as satisfactory to us in those future times, as theirs are or were to them at the time when they prevailed.

III.—Eugenic Qualities of Primary Importance

The following is offered as a contribution to the art of justly appraising the eugenic values of different qualities. It may fairly be assumed that the presence of certain inborn traits is requisite before a claim to eugenic rank can be justified, because these qualities are needed to bring out the full values of such special faculties as broadly distinguish philosophers, artists, financiers, soldiers, and other representative classes. The method adopted for discovering the qualities in question is to consider groups of individuals, and to compare the qualities that distinguish such groups as flourish or prosper from others of the same kind that decline or decay. This method has the advantage of giving results more free from the possibility of bias than those derived from examples of individual cases.

In what follows I shall use the word "community" in its widest sense, as including any group of persons who are connected by a common interest—families, schools, clubs, sects, municipalities, nations, and all intermediate social units. Whatever qualities increase the prosperity of most or every one of these, will, as I hold, deserve a place in the first rank of eugenic importance.

Most of us have experience, either by direct observation or through historical reading, of the working of several communities, and are capable of forming a correct picture in our minds of the salient characteristics of those that, on the one hand, are eminently prosperous, and of those that, on the other hand, are as eminently decadent. I have little doubt that the reader will agree with me that the members of prospering communities are, as a rule, conspicuously strenuous, and that those of decaying or decadent ones are conspicuously slack. A prosperous community is distinguished by the alertness of its members, by their busy occupations, by their taking pleasure in their work, by their doing it thoroughly, and by an honest pride in their community as a whole. The members of a decaying community are, for the most part, languid and indolent; their very gestures are dawdling and slouching, the opposite of smart. They shirk work when they can do so, and scamp what they undertake. A prosperous community is remarkable for the variety of the solid interests in which some or other of its members are eagerly engaged, but the questions that agitate a decadent community are for the most part of a frivolous order.

Prosperous communities are also notable for enjoyment of life; for though their members must work hard in order to procure the necessary luxuries of an advanced civilisation, they are endowed with so large a store of energy that, when their daily toil is over, enough of it remains unexpended to allow them to pursue their special hobbies during the remainder of the day. In a decadent community the men tire easily, and soon sink into drudgery; there is consequently much languor among them, and little enjoyment of life.

I have studied the causes of civic prosperity in various directions and from many points of view, and the conclusion at which I have arrived is emphatic, namely, that chief among those causes is a large capacity for labour—mental, bodily, or both—combined with eagerness for work. The course of evolution in animals shows that this view is correct in general. The huge lizards, incapable of rapid action, unless it be brief in duration and associated with long terms of repose, have been supplanted by birds and mammals possessed of powers of long endurance. These latter are so constituted as to require work, becoming restless and suffering in health when precluded from exertion.

We must not, however, overlook the fact that the influence of circumstance on a community is a powerful factor in raising its tone. A cause that catches the popular feeling will often rouse a potentially capable nation from apathy into action. A good officer, backed by adequate supplies of food and with funds for the regular payment of his troops, will change a regiment even of ill-developed louts and hooligans into a fairly smart and well-disciplined corps. But with better material as a foundation, the influence of a favourable environment is correspondingly increased, and is less liable to impairment whenever the environment changes and becomes less propitious. Hence, it follows that a sound mind and body, enlightened, I should add, with an intelligence above the average, and combined with a natural capacity and zeal for work, are essential elements in eugenics. For however famous a man may become in other respects, he cannot, I think, be justly termed eugenic if deficient in the qualities I have just named.

Eugenists justly claim to be true philanthropists, or lovers of mankind, and should bestir themselves in their special province as eagerly as the philanthropists, in the current and very restricted meaning of that word, have done in theirs. They should interest themselves in such families of civic worth as they come across, especially in those that are large, making friends both with the parents and the children, and showing themselves disposed to help to a reasonable degree, as opportunity may offer, whenever help is really needful. They should compare their own notes with those of others who are similarly engaged. They should regard such families as an eager horticulturist regards beds of seedlings of some rare variety of plant, but with an enthusiasm of a far more patriotic kind. For, since it has been shown that about 10 per cent. of the individuals born in one generation provide half the next generation, large families that are also eugenic may prove of primary importance to the nation and become its most valuable asset.

IV.—Practical Eugenics

The following are some views of my own relating to that large province of eugenics which is concerned with favouring the families of those who are exceptionally fit for citizenship. Consequently, little or nothing will here be said relating to what has been well termed by Dr. Saleeby "negative" eugenics, namely, the hindrance of the marriages and the production of offspring by the exceptionally unfit. The latter is unquestionably the more pressing subject, but it will soon be forced on the attention of the legislature by the recent report of the Royal Commission on the Feeble-minded.

Whatever scheme of action is proposed for adoption must be neither Utopian nor extravagant, but accordant throughout with British sentiment and practice.

By "worth" I mean the civic worthiness, or the value to the state, of a person. Speaking only for myself, if I had to classify persons according to worth, I should consider each of them under the three heads of physique, ability and character, subject to the provision that inferiority in any one of the three should outweigh superiority in the other two. I rank physique first, because it is not only very valuable in itself and allied to many other good qualities, but has the additional merit of being easily rated. Ability I place second on similar grounds, and character third, though in real importance it stands first of all.

The power of social opinion is apt to be underrated rather than overrated. Like the atmosphere which we breathe and in which we move, social opinion operates powerfully without our being conscious of its weight. Everyone knows that governments, manners, and beliefs which were thought to be right, decorous, and true at one period have been judged wrong, indecorous, and false at another; and that views which we have heard expressed by those in authority over us in early life tend to become axiomatic and unchangeable in mature life.

In circumscribed communities especially, social approval and disapproval exert a potent force. Is it, then, I ask, too much to expect that when a public opinion in favour of eugenics has once taken sure hold of such communities, the result will be manifested in sundry and very effective modes of action which are as yet untried?

Speaking for myself only, I look forward to local eugenic action in numerous directions, of which I will now specify one. It is the accumulation of considerable funds to start young couples of "worthy" qualities in their married life, and to assist them and their families at critical times. The charitable gifts to those who are the reverse of "worthy" are enormous in amount. I am not prepared to say how much of this is judiciously spent, or in what ways, but merely quote the fact to justify the inference that many persons who are willing to give freely at the prompting of a sentiment based upon compassion might be persuaded to give largely also in response to the more virile desire of promoting the natural gifts and the national efficiency of future generations.

V.—Eugenics as a Factor in Religion

Eugenics strengthen the sense of social duty in so many important particulars that the conclusions derived from its study ought to find a welcome home in every tolerant religion. It promotes a far-sighted philanthropy, the acceptance of parentage as a serious responsibility, and a higher conception of patriotism. The creed of eugenics is founded upon the idea of evolution; not on a passive form of it, but on one that can, to some extent, direct its own course.

Purely passive, or what may be styled mechanical evolution displays the awe-inspiring spectacle of a vast eddy of organic turmoil, originating we know not how, and travelling we know not whither. It forms a continuous whole, but it is moulded by blind and wasteful processes—namely, by an extravagant production of raw material and the ruthless rejection of all that is superfluous, through the blundering steps of trial and error.

The condition at each successive moment of this huge system, as it issues from the already quiet past and is about to invade the still undisturbed future, is one of violent internal commotion. Its elements are in constant flux and change.

Evolution is in any case a grand phantasmagoria, but it assumes an infinitely more interesting aspect under the knowledge that the intelligent action of the human will is, in some small measure, capable of guiding its course. Man has the power of doing this largely so far as the evolution of humanity is concerned; he has already affected the quality and distribution of organic life so widely that the changes on the surface of the earth, merely through his disforestings and agriculture, would be recognisable from a distance as great as that of the moon.

As regards the practical side of eugenics, we need not linger to reopen the unending argument whether man possesses any creative power of will at all, or whether his will is not also predetermined by blind forces or by intelligent agencies behind the veil, and whether the belief that man can act independently is more than a mere illusion.

Eugenic belief extends the function of philanthropy to future generations; it renders its action more pervading than hitherto, by dealing with families and societies in their entirety, and it enforces the importance of the marriage covenant by directing serious attention to the probable quality of the future offspring. It sternly forbids all forms of sentimental charity that are harmful to the race, while it eagerly seeks opportunity for acts of personal kindness. It strongly encourages love and interest in family and race. In brief, eugenics is a virile creed, full of hopefulness, and appealing to many of the noblest feelings of our nature.



ERNST HAECKEL

The Evolution of Man

Ernst Haeckel, who was born in Potsdam, Germany, Feb. 16, 1834, descends from a long line of lawyers and politicians. To his father's annoyance, he turned to science, and graduated in medicine. After a long tour in Italy in 1859, during which he wavered between art and science, he decided for zoology, and made a masterly study of a little-known group of sea-animalcules, the Radiolaria. In 1861 he began to teach zoology at Jena University. Darwin's "Origin of Species" had just been translated into German, and he took up the defence of Darwinism against almost the whole of his colleagues. His first large work on evolution, "General Morphology," was published in 1866. He has since published forty-two distinct works. He is not only a master of zoology, but has a good command of botany and embryology. Haeckel's "Evolution of Man" (Anthropogenie), is generally accepted as being his most important production. Published in 1874, at a time when the theory of natural evolution had few supporters in Germany, the work was hailed with a storm of controversy, one celebrated critic declaring that it was a blot on the escutcheon of Germany. From the hands of English scientists, however, the treatise received a warm welcome. Darwin said he would probably never have written his "Descent of Man" had Haeckel published his work earlier.

I.—The Science of Man

The natural history of mankind, or anthropology, must always excite the most lively interest, and no part of the science is more attractive than that which deals with the question of man's origin. In order to study this with full profit, we must combine the results of two sciences, ontogeny (or embryology) and phylogeny (the science of evolution). We do this because we have now discovered that the forms through which the embryo passes in its development correspond roughly to the series of forms in its ancestral development. The correspondence is by no means complete or precise, since the embryonic life itself has been modified in the course of time; but the general law is now very widely accepted. I have called it "the biogenetic law," and will constantly appeal to it in the course of this study.

It is only in recent times that the two sciences have advanced sufficiently to reveal the correspondence of the two series of forms. Aristotle provided a good foundation for embryology, and made some interesting discoveries, but no progress was made in the science for 2,000 years after him. Then the Reformation brought some liberty of research, and in the seventeenth century several works were written on embryology.

For more than a hundred years the science was still hampered by the lack of good microscopes. It was generally believed that all the organs of the body existed, packed in a tiny point of space, in the germ. About the middle of the eighteenth century, Caspar Friedrich Wolff discovered the true development; but his work was ignored, and it was only fifty years later that modern embryology began to work on the right line. K.E. von Baer made it clear that the fertilised ovum divides into a group of cells, and that the various organs of the body are developed from these layers of cells, in the way I shall presently describe.

The science of phylogeny, or, as it is popularly called, the evolution of species, had an equally slow growth. On the ground of the Mosaic narrative, no less than in view of the actual appearance of the living world, the great naturalist Linne (1735) set up the dogma of the unchangeability of species. Even when quite different remains of animals were discovered by the advancing science of geology, they were forced into the existing narrow framework of science by Cuvier. Sir Charles Lyell completely undid the fallacious work of Cuvier, but in the meantime the zoologists themselves were moving toward the doctrine of evolution.

Jean Lamarck made the first systematic attempt to expound the theory in his "Zoological Philosophy" (1809). He suggested that animals modified their organs by use or disuse, and that the effect of this was inherited. In the course of time these inherited modifications reached such a pitch that the organism fell into a new "species." Goethe also made some remarkable contributions to the science of evolution. But it was reserved for Charles Darwin to win an enduring place in science for the theory. "The Origin of Species" (1859) not only sustained it with a wealth of positive knowledge which Lamarck did not command, but it provided a more luminous explanation in the doctrine of natural selection. Huxley (1863) followed with an application of the law to man, and in 1866 I gave a comprehensive sketch of its application throughout the whole animal world. In 1874 I published the first edition of the present work.

The doctrine of evolution is now a vital part of biology, and we might accept the evolution of man as a special deduction from the general law. Three great groups of evidence impose that law on us. The first group consists of the facts of palaeontology, or the fossil record of past animal life. Imperfect as the record is, it shows us a broad divergence of successively changing types from a simple common root, and in some cases exhibits the complete transition from one type to another. The next document is the evidence of comparative anatomy. This science groups the forms of living animals in such a way that we seem to have the same gradual divergence of types from simple common ancestors. In particular, it discovers certain rudimentary organs in the higher animals, which can only be understood as the shrunken relics of organs that were once useful to a remote ancestor. Thus, man has still the rudiment of the third eyelid of his shark-ancestor. The third document is the evidence of embryology, which shows us the higher organism substantially reproducing, in its embryonic development, the long series of ancestral forms.

II.—Man's Embryonic Development

The first stage in the development of any animal is the tiny speck of plasm, hardly visible to the naked eye, which we call the ovum, or egg-cell. It is a single cell, recalling the earliest single-celled ancestor of all animals. In its immature form it is not unlike certain microscopic animalcules known as amoeboe. In its mature form it is about 1/125th of an inch in diameter.

When the male germ has blended with the female in the ovum, the new cell slowly divides into two, with a very complicated division of the material composing its nucleus. The two cells divide into four, the four into eight, and so on until we have a round cluster of cells, something like a blackberry in shape.

This morula, as I have called it, reproduces the next stage in the development of life. As all animals pass through it, our biogenetic law forces us to see in it an ancestral stage; and in point of fact we have animals of this type living in Nature to-day. The round cluster becomes filled with fluid, and we have a hollow sphere of cells, which I call the blastula. The corresponding early ancestor I name the Blastaea, and again we find examples of it, like the Volvox of the ponds, in Nature to-day.

The next step is very important. The hollow sphere closes in on itself, as when an india rubber ball is pressed into the form of a cup. We have then a vase-shaped body with two layers of cells, an inner and an outer, and an opening. The inner layer we call the entoderm, the outer the ectoderm; and the "primitive mouth" is known as the blastopore. In the higher animals a good deal of food-yolk is stored up in the germ, and so the vase-shaped structure has been flattened and altered. It has, however, been shown that all embryos pass through this stage (gastrulation), and we again infer the existence of a common ancestor of that type—the Gastraea. The lowest group of many-celled animals—the corals, jelly-fishes, and anemones—are essentially of that structure.

The embryo now consists of two layers of cells, the "germ-layers," an inner and outer. As the higher embryo develops, a third layer of cells now pushes between the two. We may say, broadly, that from this middle layer are developed most of the animal organs of the body; from the internal germ-layer is developed the lining of the alimentary canal and its dependent glands; from the outer layer are formed the skin and the nervous system—which developed originally in the skin.

The embryo of man and all the other higher animals now develops a cavity, a pair of pouches, by the folding of the layer at the primitive mouth. Sir E. Ray Lankester, and Professor Balfour, and other students, traced this formation through the whole embryonic world, and we are therefore again obliged to see in it a reminiscence of an ancestral form—a primitive worm-like animal, of a type we shall see later. The next step is the formation of the first trace of what will ultimately be the backbone. It consists at first of a membraneous tube, formed by the folding of the inner layer along the axis of the embryo-body. Later this tube will become cartilage, and in the higher animals the cartilage will give place to bone.

The other organs of the body now gradually form from the germ-layers, principally by the folding of the layers into tubes. A light area appears on the surface of the germ. A streak or groove forms along its axis, and becomes the nerve-cord running along the back. Cube-shaped structures make their appearance on either side of it; these prove to be the rudiments of the vertebrae—or separate bones of the backbone—and gradually close round the cord. The heart is at first merely a spindle-shaped enlargement of the main ventral blood-vessel. The nose is at first only a pair of depressions in the skin above the mouth.

When the human embryo is only a quarter of an inch in length, it has gill-clefts and gill-arches in the throat like a fish, and no limbs. The heart—as yet with only the simple two-chambered structure of a fish's heart—is up in the throat—as in the fish—and the principal arteries run to the gill-slits. These structures never have any utility in man or the other land-animals, though the embryo always has them for a time. They point clearly to a fish ancestor.

Later, they break up, the limbs sprout out like blunt fins at the sides, and the long tail begins to decrease. By the twelfth week the human frame is perfectly formed, though less than two inches long. Last of all, it retains its resemblance to the ape. In the embryonic apparatus, too, man closely resembles the higher ape.

III.—Our Ancestral Tree

The series of forms which we thus trace in man's embryonic development corresponds to the ancestral series which we would assign to man on the evidence of palaeontology and comparative anatomy. At one time, the tracing of this ancestral series encountered a very serious check. When we examined the groups of living animals, we found none that illustrated or explained the passage from the non-backboned—invertebrate—to the backboned—vertebrate—animals. This gap was filled some years ago by the discovery of the lancelet—Amphioxus—and the young of the sea-squirt—Ascidia. The lancelet has a slender rod of cartilage along its back, and corresponds very closely with the ideal I have sketched of our primitive backboned ancestor. It may be an offshoot from the same group. The sea-squirt further illustrates the origin of the backbone, since it has a similar rod of cartilage in its youth, and loses it, by degeneration, in its maturity.

In this way the chief difficulty was overcome, and it was possible to sketch the probable series of our ancestors. It must be well understood that not only is the whole series conjectural, but no living animal must be regarded as an ancestral form. The parental types have long been extinct, and we may, at the most, use very conservative living types to illustrate their nature, just as, in the matter of languages, German is not the parent, but the cousin of Anglo-Saxon, or Greek of Latin. The original parental languages are lost. But a language like Sanscrit survives to give us a good idea of the type.

The law of evolution is based on such a mass of evidence that we may justly draw deductions from it, where the direct evidence is incomplete. This is especially necessary in the early part of our ancestral tree, because the fossil record quite fails us. For millions of years the early soft-bodied animals left no trace in the primitive mud, which time has hardened into rocks, and we are restricted to the evidence of embryology and of comparative zoology. This suffices to give us a general idea of the line of development.

In nature to-day, one of the lowest animal forms is a tiny speck of living plasm called the amoeba. We have still more elementary forms, such as the minute particles which make up the bluish film on damp rocks, but they are of a vegetal character, or below it. They give us some idea of the very earliest forms of life; minute living particles, with no organs, down to the ten-thousandth part of an inch in diameter. The amoeba represents the lowest animal, and, as we saw, the ovum in many cases resembles an amoeba. We therefore take some such one-celled creature as our first animal ancestor. Taking food in at all parts of its surface, having no permanent organs of locomotion, and reproducing by merely splitting into two, it exhibits the lowest level of animal life.

The next step in development would be the clustering together of these primitive microbes as they divided. This is actually the stage that comes next in the development of the germ, and it is the next stage upward in the existing animal world. We assume that these clusters of microbes—or cells, as we will now call them—bent inward, as we saw the embryo do, and became two-layered, cup-shaped organisms, with a hollow interior (primitive stomach) and an aperture (primitive mouth). The inner cells now do the work of digestion alone; the outer cells effect locomotion, by means of lashes like oars, and are sensitive. This is, in the main, the structure of the next great group of animals, the hydra, coral, meduca, and anemone. They have remained at this level, though they have developed, special organs for stinging their prey and bringing the food into their mouths.

Both zoology and the appearance of the embryo point to a worm-like animal as the next stage. Constant swimming in the water would give the animal a definite head, with special groups of nerve-cells, a definite tail, and a two-sided or evenly-balanced body.

We mean that those animals would be fittest to live, and multiply most, which developed this organisation. Sense-organs would now appear in the head, in the form of simple depressions, lined with sensitive cells, as they do in the embryo; and a clump of nerve-cells within would represent the primitive brain. In the vast and varied worm-group we find illustrations of nearly every step in this process of evolution.

The highest type of worm-like creature, the acorn-headed worm—Balanoglossus—takes us an important step further. It has gill-openings for breathing, and a cord of cartilage down its back. We saw that the human embryo has a gill-apparatus, and that, comparing the lancelet and the sea-squirt, the backbone must have begun as a string of cartilage-cells. We are now on firmer ground, for there is no doubt that all the higher land-animals come from a fish ancestor. The shark, one of the most primitive of fishes in organisation, probably best suggests this ancestor to us. In fact, in the embryonic development of the human face there is a clear suggestion of the shark.

Up to this period the story of evolution had run its course in the sea. The area of dry land was now increasing, and certain of the primitive fishes adapted themselves to living on land. They walked on their fins, and used their floating-bladders—large air-bladders in the fish, for rising in the water—to breathe air. We not only have fishes of this type in Australia to-day, but we have the fossil remains of similar fishes in the Old Red Sandstone rocks. From mud-fish the amphibian would naturally develop, as it did in the coal-forest period. Walking on the fins would strengthen the main stem, the broad paddle would become useless, and we should get in time the bony five-toed limb. We have many of these giant salamander forms in the rocks.

The reptile now evolved from the amphibian, and a vast reptile population spread over the earth. From one of these early reptiles the birds were evolved. Geology furnishes the missing link between the bird and the reptile in the Archaeopteryx, a bird with teeth, claws on its wings, and a reptilian tail. From another primitive reptile the important group of the mammals was evolved. We find what seem to be the transitional types in the rocks of South Africa. The scales gave way to tufts of hair, the heart evolved a fourth chamber, and thus supplied purer blood (warm blood), the brain profited by the richer food, and the mother began to suckle the young. We have still a primitive mammal of this type in the duck-mole, or duck-billed platypus (Ornithorhyncus) of Australia. There are grounds for thinking that the next stage was an opossum-like animal, and this led on to the lowest ape-like being, the lemur. Judging from the fossil remains, the black lemur of Madagascar best suggests this ancestor.

The apes of the Old and New Worlds now diverged from this level, and some branch of the former gave rise to the man-like apes and man. In bodily structure and embryonic development the large apes come very close to man, and two recent discoveries have put their blood-relationship beyond question. One is that experiments in the transfusion of blood show that the blood of the man-like ape and man have the same action on the blood of lower animals. The other is that we have discovered, in Java, several bones of a being which stands just midway between the highest living ape and lowest living race of men. This ape-man (Pithecanthropus) represents the last of our animal and first of our human ancestors.

IV.—Evolution of Separate Organs

So far, we have seen how the human body as a whole develops through a long series of extinct ancestors. We may now take the various systems of organs one by one, and, if we are careful to consult embryology as well as zoology, we can trace the manner of their development. It is, in accordance with our biogenetic law, the same in the embryo, as a rule, as in the story of past evolution.

We take first the nervous system. In the lowest animals, as in the early stages of the embryo, there are no nerve-cells. In the embryo the nerve-cells develop from the outer, or skin layer, of cells. This, though strange as regards the human nervous system, is a correct preservation of the primitive seat of the nerves. It was the surface of the animal that needed to be sensitive in the primitive organism. Later, when definite connecting nerves were formed, only special points in the surface, protected by coverings which did not interfere with the sensitiveness, needed to be exposed, and the nerves transmitted the impressions to the central brain.

This development is found in the animal world to-day. In such animals as the hydra we find the first crude beginning of unorganised nerve-cells. In the jelly-fish we find nerve-cells clustered into definite sensitive organs. In the lower worms we have the beginning of organs of smell and vision. They are at first merely blind, sensitive pits in the skin, as in the embryo. The ear has a peculiar origin. Up to the fish level there is no power of hearing. There is merely a little stone rolling in a sensitive bed, to warn the animal of its movement from side to side. In the higher animals this evolves into the ear.

The glands of the skin (sweat, fat, tears, etc.) appear at first as blunt, simple ingrowths. The hair first appears in tufts, representing the scales, from underneath which they were probably evolved. The thin coat of hair on the human body to-day is an ancestral inheritance. This is well shown by the direction of the hairs on the arm. As on the ape's arm, both on the upper and lower arm, they grow toward the elbow. The ape finds this useful in rain, using his arms like a thatched roof, and on our arm this can only be a reminiscence of the habits of an ape ancestor.

We have seen how the spinal cord first appears as a tube in the axis of the back, and the cartilaginous column closes round it. All bone appears first as membrane, then cartilage, and finally ossifies. This is the order both in past evolution and in present embryonic development. The brain is at first a bulbous expansion of the spinal nerve-cord. It is at first simple, but gradually, both in the scale of nature and in the embryo, divides into five parts. One of these parts, the cerebrum, is mainly connected with mental life. We find it increasing in size, in proportion to the animal's intelligence, until in man it comes to cover the whole of the brain. When we remove it from the head of the mammal, without killing the animal, we find all mental life suspended, and the whole vitality used in vegetative functions.

In the evolution of the bony system we find the same correspondence of embryology and evolution. The main column is at first a rod of cartilage. In time the separate cubes appear which are to form the vertebrae of the flexible column. The skull develops in the same way. Just as the brain is a specially modified part of the nerve-rod, the skull is only a modified part of the vertebral column. The bones that compose it are modified vertebrae, as Goethe long ago suspected. The skull of the shark gives us a hint of the way in which the modification took place, and the formation of the skull in the embryo confirms it.

That adult man is devoid of that prolongation of the vertebral column which we call a tail is not a distinctive peculiarity. The higher apes are equally without it. We find, however, that the human embryo has a long tail, much longer than the legs, when they are developing. At times, moreover, children are born with tails—perfect tails, with nerves and muscles, which they move briskly under emotion, and these have to be amputated. The development of the limb from the fin offers no serious difficulty to the osteologist. All the higher animals descend from a five-toed ancestor. The whale has taken again to the water, and reconverted its limb into a paddle. The bones of the front feet still remain under the flesh. Animals of the horse type have had the central toe strengthened, for running purposes, at the expense of the rest. The serpent has lost its limbs from disuse, but in the python a rudimentary limb-bone is still preserved.

The alimentary system, blood-vessel system, and reproductive system have been evolved gradually in the same way. The stomach is at first the whole cavity in the animal. Later it becomes a straight, simple tube, strengthened by a gullet in front. The liver is an outgrowth from this tube; the stomach proper is a bulbous expansion of its central part, later provided with a valve. The kidneys are at first simple channels in the skin for drainage, then closed tubes, which branch out more and more, and then gather into our compact kidneys. We thus see that the building up of the human body from a single cell is a substantial epitome of the long story of evolution, which occupied many millions of years. We find man bearing in his body to-day traces of organs which were useful to a remote ancestor, but of no advantage, and often a source of mischief to himself. We learn that the origin of man, instead of being placed a few thousand years ago, must be traced back to the point where, hundreds of thousands of years ago, he diverged from his ape-cousins, though he retains to-day the plainest traces of that relationship. Body and mind—for the development of mind follows with the utmost precision on the development of brain—he is the culmination of a long process of development. His spirit is a form of energy inseparably bound up with the substance of his body. His evolution has been controlled by the same "eternal, iron laws" as the development of any other body—the laws of heredity and adaptation.



WILLIAM HARVEY

On the Motion of the Heart and Blood

William Harvey, the discoverer of the circulation of the blood, was born at Folkestone, England, on April 1, 1578. After graduating from Caius College, Cambridge, he studied at Padua, where he had the celebrated anatomist, Fabricius of Aquapendente, for his master. In 1615 he was elected Lumleian lecturer at the College of Physicians, and three years later was appointed physician extraordinary to King James I. In 1628, twelve years after his first statement of it in his lectures, he published at Frankfurt, in Latin, "An Anatomical Disquisition on the Motion of the Heart and Blood," in which he maintained that there is a circulation of the blood. Moreover, he distinguished between the pulmonary circulation, from the right side of the heart to the left through the lungs, and the systemic circulation from the left side of the heart to the right through the rest of the body. Further, he maintained that it was the office of the heart to maintain this circulation by its alternate diastole (expansion) and systole (contraction) throughout life. This discovery was, says Sir John Simon, the most important ever made in physiological science. It is recorded that after his publication of it Harvey lost most of his practice. Harvey died on June 3, 1657.

I.—Motions of the Heart in Living Animals

When first I gave my mind to vivisections as a means of discovering the motions and uses of the heart, I found the task so truly arduous that I was almost tempted to think, with Fracastorius, that the motion of the heart was only to be comprehended by God. For I could neither rightly perceive at first when the systole and when the diastole took place, nor when and where dilation and contraction occurred, by reason of the rapidity of the motion, which, in many animals, is accomplished in the twinkling of an eye, coming and going like a flash of lightning. At length it appeared that these things happen together or at the same instant: the tension of the heart, the pulse of its apex, which is felt externally by its striking against the chest, the thickening of its walls, and the forcible expulsion of the blood it contains by the constriction of its ventricles.

Hence the very opposite of the opinions commonly received appears to be true; inasmuch as it is generally believed that when the heart strikes the breast and the pulse is felt without, the heart is dilated in its ventricles and is filled with blood. But the contrary of this is the fact; that is to say, the heart is in the act of contracting and being emptied. Whence the motion, which is generally regarded as the diastole of the heart, is in truth its systole. And in like manner the intrinsic motion of the heart is not the diastole but the systole; neither is it in the diastole that the heart grows firm and tense, but in the systole; for then alone when tense is it moved and made vigorous. When it acts and becomes tense the blood is expelled; when it relaxes and sinks together it receives the blood in the manner and wise which will by and by be explained.

From divers facts it is also manifest, in opposition to commonly received opinions, that the diastole of the arteries corresponds with the time of the heart's systole; and that the arteries are filled and distended by the blood forced into them by the contraction of the ventricles. It is in virtue of one and the same cause, therefore, that all the arteries of the body pulsate, viz., the contraction of the left ventricle in the same way as the pulmonary artery pulsates by the contraction of the right ventricle.

I am persuaded it will be found that the motion of the heart is as follows. First of all, the auricle contracts and throws the blood into the ventricle, which, being filled, the heart raises itself straightway, makes all its fibres tense, contracts the ventricles and performs a beat, by which beat it immediately sends the blood supplied to it by the auricle into the arteries; the right ventricle sending its charge into the lungs by the vessel called vena arteriosa, but which, in structure and function, and all things else, is an artery; the left ventricle sending its charge into the aorta, and through this by the arteries to the body at large.

The grand cause of hesitation and error in this subject appears to me to have been the intimate connection between the heart and the lungs. When men saw both the pulmonary artery and the pulmonary veins losing themselves in the lungs, of course it became a puzzle to them to know how the right ventricle should distribute the blood to the body, or the left draw it from the venae cavae. Or they have hesitated because they did not perceive the route by which the blood is transferred from the veins to the arteries, in consequence of the intimate connection between the heart and lungs. And that this difficulty puzzled anatomists not a little when in their dissections they found the pulmonary artery and left ventricle full of black and clotted blood, plainly appears when they felt themselves compelled to affirm that the blood made its way from the right to the left ventricle by sweating through the septum of the heart.

Had anatomists only been as conversant with the dissection of the lower animals as they are with that of the human body, the matters that have hitherto kept them in perplexity of doubt would, in my opinion, have met them freed from every kind of difficulty. And first in fishes, in which the heart consists of but a single ventricle, they having no lungs, the thing is sufficiently manifest. Here the sac, which is situated at the base of the heart, and is the part analogous to the auricle in man, plainly throws the blood into the heart, and the heart in its turn conspicuously transmits it by a pipe or artery, or vessel analogous to an artery; these are facts which are confirmed by simple ocular experiment. I have seen, farther, that the same thing obtained most obviously.

And since we find that in the greater number of animals, in all indeed at a certain period of their existence, the channels for the transmission of the blood through the heart are so conspicuous, we have still to inquire wherefore in some creatures—those, namely, that have warm blood and that have attained to the adult age, man among the number—we should not conclude that the same thing is accomplished through the substance of the lungs, which, in the embryo, and at a time when the functions of these organs is in abeyance, Nature effects by direct passages, and which indeed she seems compelled to adopt through want of a passage by the lungs; or wherefore it should be better (for Nature always does that which is best) that she should close up the various open routes which she had formerly made use of in the embryo, and still uses in all other animals; not only opening up no new apparent channels for the passage of the blood therefore, but even entirely shutting up those which formerly existed in the embryos of those animals that have lungs. For while the lungs are yet in a state of inaction, Nature uses the two ventricles of the heart as if they formed but one for the transmission of the blood. The condition of the embryos of those animals which have lungs is the same as that of those animals which have no lungs.

Thus, by studying the structure of the animals who are nearer to and further from ourselves in their modes of life and in the construction of their bodies, we can prepare ourselves to understand the nature of the pulmonary circulation in ourselves, and of the systemic circulation also.

II.—Systemic Circulation

What remains to be said is of so novel and unheard of a character that I not only fear injury to myself from the envy of a few, but I tremble lest I have mankind at large for my enemies, so much do wont and custom that become as another nature, and doctrine once sown that hath struck deep root, and respect for antiquity, influence all men.

And, sooth to say, when I surveyed my mass of evidence, whether derived from vivisections and my previous reflections on them, or from the ventricles of the heart and the vessels that enter into and issue from them, the symmetry and size of these conduits—for Nature, doing nothing in vain, would never have given them so large a relative size without a purpose; or from the arrangement and intimate structure of the valves in particular and of the many other parts of the heart in general, with many things besides; and frequently and seriously bethought me and long revolved in my mind what might be the quantity of blood which was transmitted, in how short a time its passage might be effected and the like; and not finding it possible that this could be supplied by the juices of the ingested aliment without the veins on the one hand becoming drained, and the arteries on the other getting ruptured through the excessive charge of blood, unless the blood should somehow find its way from the arteries into the veins, and so return to the right side of the heart; when I say, I surveyed all this evidence, I began to think whether there might not be a motion as it were in a circle.

Now this I afterwards found to be true; and I finally saw that the blood, forced by the action of the left ventricle into the arteries, was distributed to the body at large, and its several parts, in the same manner as it is sent through the lungs, impelled by the right ventricle into the pulmonary artery; and that it then passed through the veins and along the vena cava, and so round to the left ventricle in the manner already indicated; which motion we may be allowed to call circular, in the same way as Aristotle says that the air and the rain emulate the circular motion of the superior bodies. For the moist earth, warmed by the sun, evaporates; the vapours drawn upwards are condensed, and descending in the form of rain moisten the earth again. And by this arrangement are generations of living things produced; and in like manner, too, are tempests and meteors engendered by the circular motion of the sun.

And so in all likelihood does it come to pass in the body through the motion of the blood. The various parts are nourished, cherished, quickened by the warmer, more perfect, vaporous, spirituous, and, as I may say, alimentive blood; which, on the contrary, in contact with these parts becomes cooled, coagulated, and, so to speak, effete; whence it returns to its sovereign, the heart, as if to its source, or to the inmost home of the body, there to recover its state of excellence or perfection. Here it resumes its due fluidity, and receives an infusion of natural heat—powerful, fervid, a kind of treasury of life—and is impregnated with spirits and, it might be said, with balsam; and thence it is again dispersed. And all this depends upon the motion and action of the heart.

Confirmations of the Theory

Three points present themselves for confirmation, which, being established, I conceive that the truth I contend for will follow necessarily and appear as a thing obvious to all.

The first point is this. The blood is incessantly transmitted by the action of the heart from the vena cava to the arteries in such quantity that it cannot be supplied from the ingesta, and in such wise that the whole mass must very quickly pass through the organ.

Let us assume the quantity of blood which the left ventricle of the heart will contain when distended to be, say, two ounces (in the dead body I have found it to contain upwards of two ounces); and let us suppose, as approaching the truth, that the fourth part of its charge is thrown into the artery at each contraction. Now, in the course of half an hour the heart will have made more than one thousand beats. Multiplying the number of drachms propelled by the number of pulses, we shall have one thousand half-ounces sent from this organ into the artery; a larger quantity than is contained in the whole body. This truth, indeed, presents itself obviously before us when we consider what happens in the dissection of living animals. The great artery need not be divided, but a very small branch only (as Galen even proves in regard to man), to have the whole of the blood in the body, as well that of the veins as of the arteries, drained away in the course of no long time—some half hour or less.

The second point is this. The blood, under the influence of the arterial pulse, enters, and is impelled in a continuous, equable, and incessant stream through every part and member of the body in much larger quantity than were sufficient for nutrition, or than the whole mass of fluids could supply.

I have here to cite certain experiments. Ligatures are either very tight or of middling tightness. A ligature I designate as tight, or perfect, when it is drawn so close about an extremity that no vessel can be felt pulsating beyond it. Such ligatures are employed in the removal of tumours; and in these cases, all afflux of nutriment and heat being prevented by the ligature, we see the tumours dwindle and die, and finally drop off. Now let anyone make an experiment upon the arm of a man, either using such a fillet as is employed in bloodletting, or grasping the limb tightly with his hand; let a ligature be thrown about the extremity and drawn as tightly as can be borne. It will first be perceived that beyond the ligature the arteries do not pulsate, while above it the artery begins to rise higher at each diastole and to swell with a kind of tide as it strove to break through and overcome the obstacle to its current.

Then let the ligature be brought to that state of middling tightness which is used in bleeding, and it will be seen that the hand and arm will instantly become deeply suffused and extended, and the veins show themselves tumid and knotted. Which is as much as to say that when the arteries pulsate the blood is flowing through them, but where they do not pulsate they cease from transmitting anything. The veins again being compressed, nothing can flow through them; the certain indication of which is that below the ligature they are much more tumid than above it.

Whence is this blood? It must needs arrive by the arteries. For that it cannot flow in by the veins appears from the fact that the blood cannot be forced towards the heart unless the ligature be removed. Further, when we see the veins below the ligature instantly swell up and become gorged when from extreme tightness it is somewhat relaxed, the arteries meanwhile continuing unaffected, this is an obvious indication that the blood passes from the arteries into the veins, and not from the veins into the arteries, and that there is either an anastomosis of the two orders of vessels, or pores in the flesh and solid parts generally that are permeable to the blood.

And now we understand wherefore in phlebotomy we apply our fillet above the part that is punctured, not below it. Did the flow come from above, not from below, the bandage in this case would not only be of no service, but would prove a positive hindrance. And further, if we calculate how many ounces flow through one arm or how many pass in twenty or thirty pulsations under the medium ligature, we shall perceive that a circulation is absolutely necessary, seeing that the quantity cannot be supplied immediately from the ingesta, and is vastly more than can be requisite for the mere nutrition of the parts.

And the third point to be confirmed is this. That the veins return this blood to the heart incessantly from all parts and members of the body.

This position will be made sufficiently clear from the valves which are found in the cavities of the veins themselves, from the uses of these, and from experiments cognisable by the senses. The celebrated Hieronymus Fabricius, of Aquapendente, first gave representations of the valves in the veins, which consist of raised or loose portions of the inner membranes of these vessels of extreme delicacy and a sigmoid, or semi-lunar shape. Their office is by no means explained when we are told that it is to hinder the blood, by its weight, from flowing into inferior parts; for the edges of the valves in the jugular veins hang downwards, and are so contrived that they prevent the blood from rising upwards.

The valves, in a word, do not invariably look upwards, but always towards the trunks of the veins—towards the seat of the heart. They are solely made and instituted lest, instead of advancing from the extreme to the central parts of the body, the blood should rather proceed along the veins from the centre to the extremities; but the delicate valves, while they readily open in the right direction, entirely prevent all such contrary motion, being so situated and arranged that if anything escapes, or is less perfectly obstructed by the flaps of the one above, the fluid passing, as it were, by the chinks between the flaps, it is immediately received on the convexity of the one beneath, which is placed transversely with reference to the former, and so is effectually hindered from getting any farther. And this I have frequently experienced in my dissections of veins. If I attempted to pass a probe from the trunk of the veins into one of the smaller branches, whatever care I took I found it impossible to introduce it far any way by reason of the valves; whilst, on the contrary, it was most easy to push it along in the opposite direction, from without inwards, or from the branches towards the trunks and roots.

And now I may be allowed to give in brief my view of the circulation of the blood, and to propose it for general adoption.

The Conclusion

Since all things, both argument and ocular demonstration, show that the blood passes through the lungs and heart by the action of the ventricles; and is sent for distribution to all parts of the body, where it makes its way into the veins and pores of the flesh; and then flows by the veins from the circumference on every side to the centre, from the lesser to the greater veins; and is by them finally discharged into the vena cava and right auricle of the heart, and this in such a quantity or in such a flux and reflux, thither by the arteries, hither by the veins, as cannot possibly be supplied by the ingesta, and is much greater than can be required for mere purposes of nutrition; therefore, it is absolutely necessary to conclude that the blood in the animal body is impelled in a circle and is in a state of ceaseless motion; and that this is the act, or function, which the heart performs by means of its pulse, and that it is the sole and only end of the motion and contraction of the heart. For it would be very difficult to explain in any other way to what purpose all is constructed and arranged as we have seen it to be.



SIR JOHN HERSCHEL

Outlines of Astronomy

Sir John Frederick William Herschel, only child—and, as an astronomer, almost the only rival—of Sir William Herschel, was born at Slough, in Ireland, on March 7, 1792. At first privately educated, in 1813 he graduated from St. John's College, Cambridge, as senior wrangler and first Smith's prizeman. He chose the law as his profession; but in 1816 reported that, under his father's direction, he was going "to take up stargazing." He then began a re-examination of his father's double stars. In 1825 he wrote that he was going to take nebulae under his especial charge. He embarked in 1833 with his family for the Cape; and his work at Feldhausen, six miles from Cape Town, marked the beginning of southern sidereal astronomy. The result of his four years' work there was published in 1847. From 1855 he devoted himself at Collingwood to the collection and revival of his father's and his own labours. His "Outlines of Astronomy," published in 1849, and founded on an earlier "Treatise on Astronomy" of 1833, was an outstanding success. Herschel's long and happy life, every day of which added its share to his scientific services, came to an end on May 11, 1871.

I.—The Wonders of the Milky Way

There is no science which draws more largely than does astronomy on that intellectual liberality which is ready to adopt whatever is demonstrated or concede whatever is rendered highly probable, however new and uncommon the points of view may be in which objects the most familiar may thereby become placed. Almost all its conclusions stand in open and striking contradiction with those of superficial and vulgar observation, and with what appears to everyone the most positive evidence of his senses.

There is hardly anything which sets in a stronger light the inherent power of truth over the mind of man, when opposed by no motives of interest or passion, than the perfect readiness with which all its conclusions are assented to as soon as their evidence is clearly apprehended, and the tenacious hold they acquire over our belief when once admitted.

If the comparison of the apparent magnitude of the stars with their number leads to no immediately obvious conclusion, it is otherwise when we view them in connection with their local distribution over the heavens. If indeed we confine ourselves to the three or four brightest classes, we shall find them distributed with a considerable approach to impartiality over the sphere; a marked preference, however, being observable, especially in the southern hemisphere, to a zone or belt passing through epsilon Orionis and alpha Crucis. But if we take in the whole amount visible to the naked eye we shall perceive a great increase of numbers as we approach the borders of the Milky Way. And when we come to telescopic magnitudes we find them crowded beyond imagination along the extent of that circle and of the branches which it sends off from it; so that, in fact, its whole light is composed of nothing but stars of every magnitude from such as are visible to the naked eye down to the smallest points of light perceptible with the best telescopes.

These phenomena agree with the supposition that the stars of our firmament, instead of being scattered indifferently in all directions through space, form a stratum of which the thickness is small in comparison with its length and breadth; and in which the earth occupies a place somewhere about the middle of its thickness and near the point where it subdivides into two principal laminae inclined at a small angle to each other. For it is certain that to an eye so situated the apparent density of the stars, supposing them pretty equally scattered through the space they occupy, would be least in the direction of the visual ray perpendicular to the lamina, and greatest in that of its breadth; increasing rapidly in passing from one to the other direction, just as we see a slight haze in the atmosphere thickening into a decided fog-bank near the horizon by the rapid increase of the mere length of the visual ray.

Such is the view of the construction of the starry firmament taken by Sir William Herschel, whose powerful telescopes first effected a complete analysis of this wonderful zone, and demonstrated the fact of its entirely consisting of stars.

So crowded are they in some parts of it that by counting the stars in a single field of his telescope he was led to conclude that 50,000 had passed under his review in a zone two degrees in breadth during a single hour's observation. The immense distances at which the remoter regions must be situated will sufficiently account for the vast predominance of small magnitudes which are observed in it.

The process of gauging the heavens was devised by Sir William Herschel for this purpose. It consisted simply in counting the stars of all magnitudes which occur in single fields of view, of fifteen minutes in diameter, visible through a reflecting telescope of 18 inches aperture, and 20 feet focal length, with a magnifying power of 180 degrees, the points of observation being very numerous and taken indiscriminately in every part of the surface of the sphere visible in our latitudes.

On a comparison of many hundred such "gauges," or local enumerations, it appears that the density of starlight (or the number of stars existing on an average of several such enumerations in any one immediate neighbourhood) is least in the pole of the Galactic circle [i.e., the great circle to which the course of the Milky Way most nearly conforms: gala = milk], and increases on all sides down to the Milky Way itself, where it attains its maximum. The progressive rate of increase in proceeding from the pole is at first slow, but becomes more and more rapid as we approach the plane of that circle, according to a law from which it appears that the mean density of the stars in the galactic circle exceeds, in a ratio of very nearly 30 to 1, that in its pole, and in a proportion of more than 4 to 1 that in a direction 15 degrees inclined to its plane.

As we ascend from the galactic plane we perceive that the density decreases with great rapidity. So far we can perceive no flaw in this reasoning if only it be granted (1) that the level planes are continuous and of equal density throughout; and (2) that an absolute and definite limit is set to telescopic vision, beyond which, if stars exist, they elude our sight, and are to us as if they existed not. It would appear that, with an almost exactly similar law of apparent density in the two hemispheres, the southern were somewhat richer in stars than the northern, which may arise from our situation not being precisely in the middle of its thickness, but somewhat nearer to its northern surface.

II.—Penetrating Infinite Space

When examined with powerful telescopes, the constitution of this wonderful zone is found to be no less various than its aspect to the naked eye is irregular. In some regions the stars of which it is composed are scattered with remarkable uniformity over immense tracts, while in others the irregularity of their distribution is quite as striking, exhibiting a rapid succession of closely clustering rich patches separated by comparatively poor intervals, and indeed in some instances absolutely dark and completely void of any star even of the smallest telescopic magnitude. In some places not more than 40 or 50 stars on an average occur in a "gauge" field of 15 minutes, while in others a similar average gives a result of 400 or 500.

Nor is less variety observable in the character of its different regions in respect of the magnitude of the stars they exhibit, and the proportional numbers of the larger and smaller magnitudes associated together, than in respect of their aggregate numbers. In some, for instance, extremely minute stars, though never altogether wanting, occur in numbers so moderate as to lead us irresistibly to the conclusion that in these regions we are fairly through the starry stratum, since it is impossible otherwise (supposing their light not intercepted) that the numbers of the smaller magnitudes should not go on increasing ad infinitum.

Previous Part     1  2  3  4  5  6  7     Next Part
Home - Random Browse