ble in the cavity of the uterus after intercourse -what that prolific contagion or prime conception is ; whether it is cor- poreal and laid up within the female, or is incorporeal ; whether the conception of the uterus be of the same nature or not with the conceptions of the brain, and fecundity be acquired in the same way as knowledge a conclusion, in favour of which there is no lack of arguments ; or, as motion and the animal opera- tions, which we call appetites, derive their origin from the conceptions of the brain, may not the natural motions and the operations of the vegetative principle, and particularly genera- tion, depend on the conception of the uterus? And then we have to inquire how this prolific contagion is of a mixed nature, and is imparted by the male to the female, and by her is transferred to the ovum ? Finally, how the contagious prin- ciple of all diseases and preternatural affections spreads insen- sibly, and is propagated?
EXERCISE THE FIFTY-FIRST.
Of the order of generation ; and, first, of the primary genital particle.
IT will be our business, by and by, when we come to treat of the matter in especial, to show what happens to the female from a fruitful embrace ; what it is that remains with her after this, and which we have still spoken of under the name of con- tagion, by which, as by a kind of infection, she conceives, and an embryo subsequently begins to grow of its own accord. Mean- time, we shall discourse of those things that manifestly appear in connexion with the organs of generation which seem most worthy of particular comment.
And first, since it appears certain that the chick is produced by epigenesis, or addition of the parts that successively arise, we shall inquire what part is formed first, before any of the rest appear, and what may be observed of this and its particular mode of generation.
What Aristotle * says of the generation of the more perfect
1 De Gen. Aniin. lib. ii, cap. 1.
