It is quite a number of years since Fritsch, in his studies of the anthropology of South Africa, pointed out that a peculiar difference exists in the form of the body of the Bushman and the Hottentot as compared to that of Europeans, in that the former exhibit slenderer forms of the bones, that the bone is very solid in its structure; while in the European the skeleton appears heavier, but of more open structure. Similar differences may be observed in a comparison between the skeletons of wild animals and those of domesticated animals; and this observation has led to the conclusion that the Bushmen are in their physical habitus to a certain extent like wild animals, while the Europeans resemble in their structure domesticated animals. This point of view—namely, that the human race in its civilized forms must be compared, not with the forms of wild animals, but rather with those of domesticated animals—seems to me a very important one; and a somewhat detailed study of the conditions in which various races are found suggests that at the present time, even among the most primitive types of man, changes incident to domestication have taken place almost all over the world. There are three different types of changes due to domestication which must be clearly distinguished. On the one hand, the bodies of domesticated animals undergo considerable transformations, owing to the change in nutrition and use of the body. On the other hand, selection and crossing have played an important part in the development of races of domesticated animals. Some changes of the former class are due to the more regular and more ample nutrition; other changes are due to modifications of the kinds of food which the domesticated animal uses when compared with the wild animal of the same species; still others are due to the different manner in which the muscular and the nervous systems are put into use. These changes are not quite the same among carnivorous and among herbivorous animals. The dog and the cat, for instance, are fairly regularly fed when they are found in domestication; but the food which is given to them is of a quite different character from the food which the wild dog and cat eat. Even among people whose diet consists almost entirely of meat, dogs are generally fed with boiled meat, or rather with the boiled, less nutritious parts of animals; while, among other tribes which utilize to a great extent vegetable food, dogs are often fed with mush and other vegetable material. The same is true of our cats, whose diet is not by any means entirely a meat diet. The exertions which wild carnivorous animals undergo to obtain food are incomparably greater than those of domesticated carnivorous animals; and it is obvious that for this reason the muscular system and the central nervous system may undergo considerable changes.