Page:Greek Biology and Medicine.djvu/137

 THE FINAL SYSTEM: GALEN is directed by Nature; for those which are distended by us undergo this distension in one direction but grow less in the others. . . . Thus Nature alone has the power to expand a body in all directions so that it remains unruptured and preserves completely its previous form." As for nutrition, the third of these great faculties: "When the matter which flows to each part of the body in the form of nutri- ment is being worked up into it, this activity is nutrition, and its cause is the nutritive faculty. Of course, the kind of activity here involved is also an alteration, but not like that occurring in the stage of genesis. For in [genesis] something comes into existence which did not exist previously, while in nutrition the inflowing material becomes assimilated to that which has already come into existence. There- fore the former kind of alteration has been termed genesis and the latter assimilation." "^ Nowadays this description would be supple- mented, or superseded, by a description of the multiplication of the body-cells in the growth of tissue, both extra- and intra-uterine, — which we perceive and can to some extent de- scribe, but still cannot account for, save as a power of nature. [115]