The well-known anatomist, J. F. Meckel, has asserted that the depression in the head of the femur (_fovea capitis_), which serves for the insertion of the round ligament (_ligamentum teres_), is absent in the chimpanzee and orang, and he adds that it is also absent in the gibbon. In a skeleton of a young chimpanzee which had not shed its milk-teeth, and of which the ligaments were also preserved, Welcker found a fully developed round ligament inserted almost in the centre of the head of the femur. This agrees in every particular with the same formation in man. On the other hand, no trace of a round ligament was to be found in the hip-joint of a young orang-utan. The cartilaginous envelope of the head of the femur was smooth throughout, without any indication of a place for inserting the ligament. Welcker again found no such depression in the femur of an aged male orang-utan, nor was there any trace of it in another aged male orang, designated as _Simia Morio_. Welcker believes that he has established the fact that the round ligament is wanting in the orang-utan, but that it is present in the gorilla, chimpanzee, and gibbon. The same naturalist remarks that, although we may certainly assume that the round ligament is absent wherever there is no depression in the head of the femur, yet the existence of such a depression in the acetabulum (_fovea acetabuli_) is not enough to prove that a round ligament was inserted in it. The innominate bones of an adult orang-utan were examined by Welcker, and displayed a small, but well-defined depression, as if destined for a receptacle for this ligament,[63] running from the cotyloid notch down to the bottom of the acetabulum, between the two horns of the semilunar-shaped articular cartilage.