Page:The Works of William Harvey (part 1 of 2).djvu/433

 endowed with plastic power, grows into the eye of the egg and the colliquament, from which and in which the primordial or rudimentary parts of the chick, the blood, to wit, and the punctum saliens are engendered, nourished, and augmented, until the perfect chick is developed. Neither is Aristotle's definition of an egg correct, as a body from part of which an embryo is formed, and by part of which it is nourished, unless the philosopher is to be understood in the following manner : The egg is a body, from part of which the chick arises, not as from a special matter, but as a man grows out of a boy ; or an egg is a perfect conception from which the chick is said to be partly constituted, partly nourished ; or to conclude, an egg is a body, the fluids of which serve both for the matter and the nourishment of the parts of the foetus. In this sense, indeed, Aristotle 1 teaches us that the matter of the human foetus is the menstrual blood; " which (when poured into the uterus by the veins) nature employs to a new purpose; viz., that of generation, and that a future being may arise, such as the one from which it springs ; for potentially it is already such as is the body whose secretion it is, namely, the mother/'

EXERCISE THE FORTY-FIFTH.

What is the material of the chick, and how it is formed in the egg ?

Since, then, we are of opinion, that for the acquisition of truth, we cannot rely on the theories of others, whether these rest on mere assertions, or even may have been confirmed by plau- sible arguments, except there be added thereto a diligent course of observation; we propose to show, by clearly- arranged re- marks derived from the book of nature, what is the material of the foetus, and in what manner it thence takes its origin. We have seen that one thing is made out of another (tan- quam ex materia) in two ways, and this as well in works of art, as in those of nature, and more particularly in the gene- ration of animals.

1 De Gen. Anim. HI), ii, cap. 4.