Among the simians, erroneously called monkeys, are the four kinds that constitute the anthropoid, or manlike, group of apes. In certain respects they differ from each other as much as any one of them differs from man. The four apes here alluded to and named in the order of their physical resemblance to man are: the gorilla, the chimpanzee, the orang, and the gibbon; but if placed in the order of their mental and social characteristics they stand as follows: the chimpanzee, which is next to man, the gorilla, the gibbon, and, last, the orang. It is possible, however, that it may yet be found that the gibbon is intellectually the highest of this group. As the skeleton is the framework of the physical structure, it will serve for the basis upon which to build up the comparisons; and as, on the whole, the chimpanzee is the nearest approach to man, we select and use him as the standard of comparison. The skeleton of the chimpanzee may be said to be an exact duplicate of that of man. The assertion, however, should be qualified by a few facts of minor importance; but since they are facts, they should not be ignored. The general plan, purpose, and structure of the skeletons of man and chimpanzee are the same. There is no part of the one which is not duplicated in the other, and there is no function discharged by any part of the one that is not discharged by a like part of the other. The chief point in which they differ is in the structure of one bone. To this we shall pay special attention.