Cuvier proceeded upon the principle, that every organized individual forms an entire system of its own, all the parts of which mutually correspond, and that none of these separate parts can change their forms without a corresponding change on the other parts of the same individual body. Where the viscera, for example, are so constructed as only to be fitted for the digestion of recent flesh, it is requisite that the jaws should be so formed as to fit them for devouring prey—the claws for seizing and tearing it to pieces—the teeth for cutting and dividing its flesh—the limbs or organs of motion for pursuing and overtaking it—and the organs of sense for discovering it at a distance. But under this general principle in the structure of carnivorous animals, the ingenious anatomist further discovered that there are several particular modifications, depending upon the size, the manners, and the haunts of prey for which each species is destined or fitted by nature; and that, from each of these particular modifications, there result certain differences in the more minute conformations of particular parts. Hence it follows, that there will exist distinct indications in every one of their parts, not only of the classes and orders of animals, but also of their genera and species. Thus, in order that the jaw may be well adapted for laying hold of objects, it is necessary that its condyle should have a certain form; that the resistance, the moving power, and the fulcrum, should all have a certain relative position with respect to each other. To enable the animal to carry off its prey when seized, a corresponding force is requisite in the muscles which elevate the head; and this again gives rise to a determinate form of the vertebræ to which these muscles are attached, and of the occiput into which they are inserted. The teeth of a carnivorous animal require to be sharp, in proportion to the greater or less quantity of flesh that they have to cut; their roots to be solid and strong, in proportion to the quantity and the size of the bones that have to be broken; and these conditions of structure will necessarily influence the development and form of the several parts that contribute to move the jaws.