The extensive order of apes was divided by Geoffroi, in 1812, into two sub-orders, which are still universally accepted in systematic zoology—New World and Old World monkeys, according to the hemisphere they respectively inhabit. The American “New World” monkeys are called Platyrrhinae (flat-nosed); their nose is flat, and the nostrils divergent, with a broad partition. The “Old World” monkeys, on the contrary, are called collectively Catarrhinae (narrow-nosed); their nostrils point downward, like man’s, and the dividing cartilage is narrow. A further difference between the two groups is that the tympanum is superficial in the platyrrhinae, but lies deeper, inside the petrous bone, in the catarrhinae; in the latter a long and narrow bony passage has been formed, while in the former it is still short and wide, or even altogether wanting. Finally, we have a much more important and decisive difference between the two groups in the circumstance that all the Old World monkeys have the same teeth as man—i. e., twenty deciduous and thirty-two permanent teeth (two incisors, one canine, two premolars, and three molars in each half of the jaw). The New World monkeys, on the other hand, have an additional premolar in each half-jaw, or thirty-six teeth altogether. The fact that these anatomical differences of the two simian groups are universal and conspicuous, and that they harmonize with their geographical distribution in the two hemispheres, fully authorizes a sharp systematic division of the two, as well as the phylogenetic conclusion that for a very long period (for more than a million years) the two sub-orders have been developing quite independently of each other in the western and eastern hemispheres. That is a most important point in view of the genealogy of our race; for man bears all the marks of a true catarrhina; he has descended from some extinct member of this sub-order in the Old World.
The numerous types of catarrhinae which still survive in Asia and Africa have been formed into two sections for some time—the tailed, doglike apes (the cynopitheci) and the tailless, manlike apes (the anthropomorpha). The latter are much nearer to man than the former, not only in the absence of a tail and in the general build of the body (especially of the head), but also on account of certain features which are unimportant in themselves but very significant in their constancy. The sacrum of the anthropoid ape, like that of man, is made up of the fusion of five vertebræ; that of the cynopithecus consists of three (more rarely four) sacral vertebræ. The premolar teeth of the cynopitheci are greater in length than breadth; those of the anthropomorpha are broader than they are long; and the first molar has four protuberances in the former, five in the latter. Furthermore, the outer incisor of the lower jaw is broader than the inner one in the manlike apes and man; in the doglike ape it is the smaller. Finally, there is a special significance in the fact, established by Selenka in 1890, that the anthropoid apes share with man the peculiar structure of the discoid placenta, the decidua reflexa, and the pedicle of the allantois. In fact, even a superficial comparison of the bodily structure of the anthropomorpha which still survive makes it clear that both the Asiatic (the orang-outang and the gibbous ape) and the African (the gorilla and chimpanzee) representatives of this group are nearer to man in build than any of the cynopitheci. Under the latter group we include the dog-faced papiomorpha, the baboon, and the long-tailed monkey, at a very low stage. The anatomical difference between these low papiomorpha and the most highly developed anthropoid apes is greater in every respect, whatever organ we take for comparison, than the difference between the latter and man. This instructive fact was established with great penetration by the anatomist Robert Hartmann, in his work on The Anthropoid Apes;[10] he proposed to divide the order of Simiae in a new way—namely, into the two great groups of primaria (man and the anthropoid ape) and the simiae proper, or pitheci (the rest of the catarrhinæ and all the platyrrhinæ). In any case, we have a clear proof of the close affinity of man and the anthropoid ape.
Thus comparative anatomy proves to the satisfaction of every unprejudiced and critical student the significant fact that the body of man and that of the anthropoid ape are not only peculiarly similar, but they are practically one and the same in every important respect. The same two hundred bones, in the same order and structure, make up our inner skeleton; the same three hundred muscles effect our movements; the same hair clothes our skin; the same groups of ganglionic cells build up the marvellous structure of our brain; the same four chambered heart is the central pulsometer in our circulation; the same thirty-two teeth are set in the same order in our jaws; the same salivary, hepatic, and gastric glands compass our digestive process; the same reproductive organs insure the maintenance of our race.
It is true that we find, on close examination, certain minor differences in point of size and shape in most of the organs of man and the ape; but we discover the same, or similar, differences between the higher and lower races of men, when we make a careful comparison—even, in fact, in a minute comparison of the various individuals of our own race. We find no two persons who have exactly the same size and form of nose, ears, eyes, and so forth. One has only to compare attentively these special features in many different persons in any large company to convince one’s self of the astonishing diversity of their construction and the infinite variability of specific forms. Not infrequently even two sisters are so much unlike as to make their origin from the same parents almost incredible. Yet all these individual variations do not weaken the significance of the fundamental similarity of structure; they are traceable to certain minute differences in the growth of the individual features.
[CHAPTER III]
OUR LIFE
Development of Physiology in Antiquity and the Middle Ages: Galen—Experiment and Vivisection—Discovery of the Circulation of the Blood by Harvey—Vitalism: Haller—Teleological and Vitalistic Conception of Life—Mechanical and Monistic View of the Physiological Processes—Comparative Physiology in the Nineteenth Century: Johannes Müller—Cellular Physiology: Max Verworn—Cellular Pathology: Virchow—Mammal Physiology—Similarity of all Vital Activity in Man and the Ape
It is only in the nineteenth century that our knowledge of human life has attained the dignity of a genuine, independent science; during the course of the century it has developed into one of the highest, most interesting, and most important branches of knowledge. This “science of the vital functions,” physiology, had, it is true, been regarded at a much earlier date as a desirable, if not a necessary, condition of success in medical treatment, and had been constantly associated with anatomy, the science of the structure of the body. But it was only much later, and much more slowly, than the latter that it could be thoroughly studied, as it had to contend with much more serious difficulties.
The idea of life, as the opposite of death, naturally became the subject of speculation at a very early age. In the living man, just as in other living animals, there were certain peculiar changes, especially movements, which were wanting in lifeless nature: spontaneous locomotion, the beat of the heart, the drawing of the breath, speech, and so forth. But the discrimination of such “organic movements” from similar phenomena in inorganic bodies was by no means easy, and was frequently impossible; the flowing stream, the flickering flame, the rushing wind, the falling rock, seemed to man to exhibit the same movements. It was quite natural that primitive man should attribute an independent life to these “dead” bodies. He knew no more of the real sources of movement in the one case than in the other.