Изображения страниц
PDF
EPUB

senses alone are most fallible in their conclusions. He uses them only as avenues by which impressions reach him, and he summons them as witnesses to testify before his intellect, to contradict or confirm each other, and thereby make manifest the truth. On the contrary, the crucial test of the savage is a single one, the visual test. With him seeing is believing. He is unequal to the conception that seeing may be illusory. So also, and for the same reason, it is to be observed in the uneducated, among civilized beings, that seeing is the final test of right to believe.

The educated, although they do, as admitted, possess a stock of inherited beliefs, differ in sum from the savage and the uneducated among the civilized in the important points, that they are perfectly aware that a portion of their stock of beliefs must, from the nature of things, be erroneous, that they are distrustful of their powers of reaching truth, and that they are consequently careful in arriving at conviction. This attitude of mind is the only sure foundation for advance. The world can advance on no other terms. The modern investigation into the nature which we see all around us is, as was the ancient, with most imperfect means, prompted by an inherent desire to know and to abide by the truth. The prompting has been called scientific wonder, which term truly designates the feeling with which men approach the mysteries of nature. To suppose that it is not associated in the majority of the ablest minds with a reverential attitude is to be ignorant of the glories that are unfolded, and of the effect of their contemplation.

Love of the truth, from the lowest savage, from the virago of civilization who, standing with arms akimbo, listens to gossip about her neighbors, to the one who lives in the world of microscopic beings as well as in his own, or the one who sits observant of the marshalling of the stars, is a distinctively human attribute, capable, as these extremes show, of infinite development for

good. It is developed love of truth which is leading the present great advance of civilization in science, literature, and the arts. It is this prompting which has led to investigation of the genealogy of man, the sources of his earthly being.

When we survey the whole animal world a most remarkable series of facts present themselves. We find individual life bound up in a single cell, in colonies of cells, in animals composed of a few cells, and in those composed of multitudinous cells. We find cells in the same animal producing tissue, and, while so producing, changing their forms to suit special purposes. We find in the human organism, for instance, excluding the primary, and from the first, somewhat differentiated cell called the ovum, or egg, cells which seem capable of infinite differentiation, to form bone, marrow, skin, and all other parts of the body.

Passing beyond these phenomena, we find in all the animal kingdoms strange similarities, masked by dissimilarities, of structure as representing function. We find, referring now only to the vertebrates, that even skull and brain seem to be graduated from vertebræ, one of the lowest, if not the very lowest of the vertebrates, the lancelet (amphioxus), which was classed by Cuvier as a worm, being without a head.

But now, confining ourselves strictly to the vertebrate subkingdom, lest we become involved in considerations too extended for our purpose, it is to be remarked that we find among them a distinct graduation among organs. Just as before we saw that, comparing living with extinct forms, there is reason to believe that among animals there has been a continuous related translation of one form into another, these branching off at times from some common progenitors into separate lines of descent; so, also, we find, among vertebrates, external and internal differences of structure relating to function, which seem to graduate into each other. More than that, when we come to examine at different periods of its development the embryo of the same

animal, we find singular attributes to be possessed by it apparently unnecessary to its present or prospective existence.

That all things which are known to us should present in every respect conditions the object of which is manifest, is an untenable proposition. But that all things which are known to us should not present contradictions between the main conditions observed and the main purposes of life to be subserved, is a perfectly tenable proposition, for, when there is a contradiction between those main conditions and the main purposes of the individual life, we reject those things which are in opposition to the main purposes of life, as having no relation to it. The dewclaw of the dog is not only not of service to the animal, but is of positive disservice to him, being frequently injured and causing him uneasiness. We therefore reject it as having any adapted relation to his present life, and recognize it as a rudiment of what was originally useful.

Now, the human embryo, the fœtus, does not respire through the lungs. It could not breathe through its lungs, because it is submerged in a fluid called the liquor amnii until, the period of gestation being past, birth begins. The first respiration which the newborn child makes is accompanied by a sneeze or a cry, showing the unwonted impact of air upon the lungs. It respires, as do all placental mammals, or those animals which have a placenta and suckle their young. The placenta, a vascular, temporary organ (the after-birth), conveys to the fœtus, through the umbilical cord, circulation derived from the mother, involv ing the oxygenation of its blood and the removal from it of effete matters. The umbilical cord, containing the proper arteries and veins, which cord directly connects the unborn child. with the placenta, is the only means by which circulation, respiration, and nutrition are effected in the unborn child by the circulation of the mother.

Beginning with the mother herself, we see, through embry

onic development, that the whole vagina and neighboring parts are graduated from, and still rudimentarily contain, a lower form of structure for the function of gestation and parturition. The embryo shows at every stage remarkable progression from lower forms of life, among the rest what are regarded as rudimentary branchiæ, or gills. All these, however, have, by the period of birth, become completely aborted and transformed into what we know as appropriate to man. The very same parts serve for either male or female, depending upon what course they take at a certain stage of development. What right have we, therefore, if the same parts can develop into either male or female organs, to say that other parts, having nothing to do with difference of sex, do not, when aborted in certain directions, and taking definite lines of development in other directions, indicate structure which was pre-existent in the adult being, and which must, therefore, although long discontinued, represent some of the previous history of the organism?

The majority of scientific men accept the conclusion indicated. It is believed, and with reason, as was remarked in one of the preceding chapters, that the embryo contains within itself, at different stages of its development until birth, a brief abstract and chronicle in time of the being concerned, an epitome, as it were, of its previous existence. Like all epitomes, however, this must necessarily contain a record, correct as far as it goes, but lacking fullness. It cannot be supposed that the embryo itself has not lost some of its original characteristics. What has been said elsewhere would conflict with the view that it has not undergone any change. But the history of an animal should be preserved for a far longer period, through the characteristics of embryonic life, than through those after birth. For, whereas, whatever in life after birth is not conducive to its well-being in the struggle of existence, tends to be eliminated; that which does not so especially concern life after birth would tend

to remain unchanged and recorded in the embryo. When we consider how enduring are certain post-natal useless characteristics, when they are of no great disservice, as in the case of the vermiform appendix in the human bowels, a small cul-de-sac, we may well understand how, in an embryonic feature, nature might permit the record in the embryo to remain indefinitely. It stands to reason, as was indicated, that the embryo should retain certain characteristics of an original condition indefinitely longer than the animal does after birth. But, besides, the development of the embryo proves that it has retained volumes of life-history of which the animal, just before birth and ever afterward, scarcely shows a trace. We have, therefore, in favor of this view, a probability, in this aspect of the case, amounting to a certainty.

The general anatomical correspondence between man and the highest of the anthropoid apes are such as to render conception of the graduation of man into his present form, through some similar organism, not so improbable as might at the first glance appear. But anatomy and physiology do not glance at the nature of things. They probe to the inmost recesses which they can reach in physical life, and accept only those conclusions which seem forced upon them by rigid reasoning. If we are justified in reaching any impressions from superficial examination, it is undeniable that conclusions which do not rely merely upon first impressions, but which are the fruit of long and patient study, are entitled to consideration.

Titles of all sorts have been devised by which man can be distinctly designated as entirely different from the lower animals, such as the tool-making and tool-using animal, all relating to perception of his vastly superior relative intelligence through brain, and mechanical ability through the possession of a wellorganized thumb. When, however, we come to examination of his physical characteristics, as compared with those of the

« ПредыдущаяПродолжить »