Pelasgic, and even Arab blood, than of the Celt or Saxon.” A careful comparison of different tribes leads to the conclusion, that the general phenomena of human life, or those processes which are termed the natural functions, the laws of the animal economy, are remarkably uniform, making allowance for the influence of climates, of modes of living, of localities, and of the accidents which interrupt the natural course. The age of puberty announces itself by corresponding symptoms, and that of advanced life by analogous signs of decrepitude, the decrease of the humors, the loss or decay of sight, and of the other senses, and a change in the color of the hair. All communities of men appear open to the attack of all kinds of disease, though a few haunt particular districts, and of course only prey upon those who are exposed to their invasion. In some cases, it is only the old inhabitants of these neighborhoods that are attacked, as in the instance of the _plica_ _polonica_, which afflicts the Sarmatic race on and near the banks of the Vistula, from which the German residents are in a great measure free. But this proves no specific difference between the two, but only shows that, to acquire a predisposition to certain local complaints is a work of time, and will probably appear in new settlers after the lapse of centuries. There is a well-marked variety in the constitution of nations, and in their liability to certain given disorders; but the difference between the torpid American and the irritable European is not greater than the common varieties of constitution which meet us within the bounds of the same family, and which render its different members peculiarly subject to different complaints. The conclusion to which these considerations point—that of the identity of mankind as a species—is strongly supported by the fecundity of the offspring of parents of different races. Hunter and other naturalists have advanced it as a law, that if the offspring of two individual animals belonging to different breeds is found to be capable of procreation, the parent animals—though differing from each other in some particulars—are of the same species; and if the offspring so engendered is sterile, then the races from which it descended are originally distinct. This is a position to which there are many exceptions; but it is undoubtedly true, that the energy of propagation is very defective in the product of a union of different species. Tried by this test, the inference is in favor of a common nature belonging to all mankind; for the mixture of originally far-separated human races has repeatedly resulted in a numerous population, physically equal, and in many instances superior, to either branch of the ancestral stock.