These seminal liquors are both extracts from all parts of the body, and in the mixture of them there is every thing necessary to form a certain number of males and females; and the more the animal abounds with this liquor, and the more that abounds with organic molecules, the greater is their number of young; as we have already remarked is the case with the small animals, and diminishes in the large. But to pursue our subject with greater attention, we shall first examine the particular formation of the human foetus, and afterwards return to the other animals. In the human species, as well as in large animals, the seminal liquors of the male and female do not contain a great abundance of organic molecules, and therefore seldom produce more than one at a time: the foetus is a male, if the number of the organic molecules of the male predominates in the mixture, and a female if the contrary; and it resembles the father or the mother as they happen to abound in the mixture of the two liquors. I conceive, therefore, that the seminal liquor of both are two matters equally active and necessary for generation; and this I think is sufficiently proved by my experiments, since I have seen the same moving bodies in the one as the other. I perceived that the liquor of the male enters into the matrix, where it meets with that of the female: that they have a perfect analogy, and are both not only composed of similar parts by their form, but also in their motions and actions; as we have remarked in Chap. VI. By the mixture of these two liquors I conceive the activity of the organic molecules of each is stopped, and that the actions of one counterbalance that of the other, insomuch that each particle ceasing to move, remains in the place most analogous to itself, and that they will naturally take the same position, and will dispose themselves in the same order they held in the animal body; those that came from the head will arrange themselves in the head of the foetus, those of the back the same, and so of every other part; consequently they will form a small organized being, in every thing like the animal from which they are extracted.