BONES OF TUE LOWER EXTREMITY.
The length of the femur depends on that of the metatarsus; and it bears an inverse ratio to the length of that part.
Hence it is very short in the horse, cow, &c. where the same mistakes are commonly committed in naming the parts as in the anterior extremity.
The proportions of the thigh and leg vary in different animals. The latter part exceeds the former in the human sub ject ; and the same remark may be made respecting the arm and fore-arm. These parts are nearly of the same length in the orang-outang. Some persons have af firmed that the negro forms a connecting link between the European and the orang-outang in these respects. (White, on the regular Gradation in Man and Ani mals, &c.) In some other simix the leg and fore-arm exceed the thigh and arm. In other animals, although there are some varieties, the leg is generally longer than the thigh.
The fibula is consolidated to the tibia at its lower end in the mole and rat. It only exists as a small styloid bone in the horse, and becomes anchylosed to the tibia in an old animal.
The structure of the metatarsus in the ruminating animals, and the horse, is the same with that of the metacarpus.
The tarsus of the horse is composed of six bones ; and is the part known in common language by the name of the hock.
Animals of the genus simia and lemur, instead of having a great toe placed pa rallel with the others, are furnished with a real thumb : 1. e. a part capable of being opposed to the other toes hence these animals can neither be called biped nor quadruped, but are really quadrumanous or fourhanded. They are not destined to go either on two or four extremities, but to live in trees, since their four prehen sile members enable them to climb with the-greatest facility. So that Cuvier has
denominated them " les grimpeurs pars excellence." Lecons d'Anat. Comp. vol. i. p. 493.) The prehensile tail of seve ral species is a further assistance in this way of life. The opossum, and others of the genus didelphis, have a similar struc ture with the quadrumana ; and it an swers the same purpose. Here, how ever, there is a separate thumb on the pos terior extremity only, whence Cuvier calls them pedimanes.
Man is the only animal in which the whole surface of the foot rests on the ground ; and this circumstance arises from the erect stature, which belongs exclusively to him. In the quadrumana, in the bear, hedge-hog, and shrew, (which are called by Cuvier planti grades,) the os calcis does not touch the ground.
The heel of a species of bear belong ing to this country, viz. the badger (ur sus meles) is covered with a long fur, which proves that this part cannot rest on the ground ; although the structure both of the bones and muscles of the lower extremity of this animal approach es considerably to that of man The same fact is stated of the bear itself, properly so called by the Parisian dis• sectors.
In other animals the body is sup ported upon the phalanges of the toes, as in the dog and cat ; in the horse and ruminating animals, no part touches the ground but the last phalanx. Here the elongation of the metatarsus removes the os calcis to such a distance from the toe, that it is placed midway between the trunk and hoof.