Again, the skeleton presents important characters. We ought, at least, to examine the breast, the pelvis, the bones of the limbs, etc.; but we must leave this subject, to say a word on the soft parts.
Regarded in the two extremes of humanity, the white European and the negro, the nervous system presents a fact which it is important to point out. With the first, the nervous centres—the brain and spinal cord—are relatively more voluminous. In the second, on the contrary, it is the expansions from the centres—the nerves—which are more voluminous.
The circulatory apparatus presents a balance somewhat analogous. With the white, the arterial apparatus, which carries the blood to the organs, is relatively more developed than the venous apparatus that draws the blood toward the heart.
The blood of the negro, studied in his native country, is more viscous and darker colored than that of the white. That of the creole negro of New Orleans is, on the contrary, paler and more aqueous, and recalls the blood of the anæmic. So, a simple change of habitat sometimes modifies a human race in this most profound character—in this liquid pabulum destined to penetrate and nourish all parts of the body.
III. Physiological Characters.—I shall dwell briefly on the physiological characters, and only point out two general facts, of which you will easily see the importance:
As regards all the great periods of life and all the great functions, there is an almost complete identity among all men, to whatever race they belong.
When this resemblance is not apparent, the cause is not in the nature of the races, but in the influence of conditions of existence. This is well proved by the fact that races the most widely separated resemble each other completely when they are exposed to identical conditions through a change of habitat. So, the precocity of the negro has been cited as distinguishing this race from European nations; but, when white people live for generations in hot countries, they take on the same peculiarity. The negress and the English Creole of the isles of the Gulf of Mexico are just alike in precocity.
On the contrary, the study of secondary functions shows that they vary from one group to another, and sometimes very widely. But, then, also, we see that the environment, the manners, the habits, etc., are the cause of these variations; and, again, we see races the most unlike come to resemble each other so much as to be confounded together. There are hunters of English and French descent who have the senses of sight and hearing as quick and sharp as the red-skins.
In concluding, the study of physiological characters strongly attests the fundamental unity of the human race, by throwing light on the marvellous flexibility of our organism.