detailed arguments sometimes seem but to amplify his general or introductory phrases.
It is the work of Nature to form all the parts of the animal while still in the womb, and after birth to bring the animal to its full size, and maintain it. This is a threefold effect, and the activities are three, "namely genesis, growth, and nutrition. Genesis, however, is not a simple activity of Nature, but is compounded of alteration and shaping. That is to say, in order that bone, nerve, veins, and all other [tissues] may come into existence, the underlying substance69 from which the animal springs must be altered; and in order that the substance so altered may acquire its appropriate shape and position, its cavities, outgrowths, attachments and so forth, it has to undergo a shaping or formative process."70
Then, proceeding from the partly false analogy of the semen and the seed cast into the earth, he enlarges his descriptive detail, without, of course, penetrating any further into the process itself. He next takes up the faculty of growth, which "is one of increase and expansion in length, breadth and thickness of the solid parts of the animal (those which have been subjected to the moulding or shaping
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