When Huxley published his powerful essay on "Man's Place in Nature" in 1863, he gave it a frontispiece showing the skeletons of man and the four living anthropoid apes, the Asiatic orang and gibbon, and the African chimpanzee and gorilla. Plate II. in the present work differs from this in giving two young specimens of the orang and the chimpanzee, and raising their size to correspond with the other three skeletons. Candid comparison of these five skeletons shows that they are not only very like each other generally, but are _identical_ in the structure, arrangement, and connection of all the parts. The same 200 bones compose the skeleton in man and in the four tailless anthropoid apes, our nearest relatives. The same 300 muscles serve to move the various parts of the skeleton. The same hair covers the skin; the same mammary glands provide food for the young. The same four-chambered heart acts as central pump of the circulation; the same 32 teeth are found in our jaws; the same reproductive organs maintain the species; the same groups of neurona or ganglionic cells compose the wondrous structure of the brain, and accomplish that highest function of the plasm which we call the soul, and many still believe to be an immortal entity. Huxley has thoroughly established this profound truth, and by further comparison with the lower apes and lemurs he came to formulate his important pithecometra principle: "Whatever organ we take, the differences between man and the anthropoid apes are slighter than the corresponding differences between the latter and the lower apes." If we make a superficial comparison of our skeletons of the anthropomorpha, we certainly notice a few salient differences in the size of the various parts; but these are purely quantitative, and are due to differences in growth, which in turn are caused by adaptation to different environments. There are, as is well known, similar differences between human beings; their arms are sometimes long, sometimes short; the forehead may be high or low, the hair thick or thin, and so on. These anatomic proofs of the pithecoid theory are most happily supplemented and confirmed by certain recent brilliant discoveries in physiology. Chief amongst these are the famous experiments of Dr. Hans Friedenthal at Berlin. He showed that the human blood acts poisonously on and decomposes the blood of the lower apes and other mammals, but has not that effect on the blood of the anthropoid apes.[8]