Aristotle's biology individual animal, it must direct and mould the growth and character of every part. Aristotle holds this creed, and devotes the De Partibus Animalium to its special illustration. First he shows it generally in regard to the animal's component parts. The homogeneous fluids and tissues exist for the sake of the more especially active parts or organs,*' like the eye or hand. They must possess the different properties, like fluidity, softness, or hardness, required by the organ, and of which it will present a combination. " For the hand . . . requires one property to enable it to effect pressure, and another and different property for simple prehension. For this reason the active or executive parts of the body are com- pounded out of bones, sinews, flesh and the like, but not these latter out of the former." And the relations between these two orders of parts are determined by a final cause,*^ which is the life of the whole animal. Aristotle will not flinch from the principle that this final end, the life of the whole animal, calls every part into being. It is irrational to hold the reverse, i.e., that the character or mechanical power of a part produces or de- termines that final end which is the life or
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