Aristotle's History of Animals

Chapter I

1. Some parts of animals are simple, and these can be divided into like parts, as flesh into pieces of flesh; others are compound, and cannot be divided into like parts, as the hand cannot be divided into hands, nor the face into faces. Of these some are not only called parts, but members, such as those which, though entire in themselves, are made up of other parts, as the head and the leg, the hand and the entire arm, or the trunk; for these parts are both entire in themselves, and made up of other parts.

2. All the compound parts also are made up of simple parts, the hand, for example, of flesh, and sinew, and bone. Some animals have all these parts the same, in others they are different from each other. Some of the parts are the same in form, as the nose and eye of one man is the same as the nose and eye of another man, and flesh is the same with flesh, and bone with bone. In like manner we may compare the parts of the horse, and of other animals, those parts, that is, which are the same in species, for the whole bears the same relation to the whole as the parts do to each other. And in animals belonging to the same class, the parts are the same, only they differ in excess or defect. By class, I mean such as bird or fish, for all these differ if either compared with their own class or with another, and there are many forms of birds and fishes.