testicles to produce semen, because in the stomach we find chyle, in the testes semen, so do we definitely assert that the egg is the product of the uterus of birds, because it is found in this part. The organ and seat of the generation of eggs is, therefore, intimately known and obvious to us. And farther, inasmuch as there are two uteri in birds, one superior and the other inferior, and these are considerably different from one another, and consequently perform different offices, it is in like manner clear what particular action is to be ascribed to each. The superior is devoted to the production of the yelk, the infe- rior to that of the albumen and remaining parts, or of the per- fect egg, as lies obvious to sense ; for in the superior uterus we never find aught beyond a multitude of yelks, nor in the inferior uterus, other than entire and perfect eggs. But these are not all the functions of the uteri as it appears, but the following are farther to be noted and enumerated, viz. : the in- crease of the egg, which succeeds immediately upon its pro- duction, and proceeds until it is perfected and acquires its proper dimensions. For the fowl does not naturally lay an egg until it has become complete and has acquired its due dimen- sions. The actions of the uteri are consequently the increase as well as the engenderment of the egg; but increase supposes and includes nutrition, as is obvious. And since all generation is the effect of the concurrence of two, viz., the agent and the matter, the agent in the generation of an egg is nothing else than the instruments or organs aforesaid, to wit, the double uterus ; and the matter is nothing but the blood."
Now whilst I admit the action of the uterus to be in a manner the generation of the egg, I by no means allow that the egg is nourished and increased by this organ. And this, both for the reasons already alleged by us when we treated of the vital principle of the egg, which is that which nourishes it, and also because it appears little likely (according to Aristotle, 1 it is impossible,) that all the internal parts of the egg, in all their dimensions, should be fashioned and made to increase by an external agent, such as the uterus is with reference to the egg ; for how, I beseech you, can that which is extrinsic ar-
1 Gener. Anim. lib. ii, cap. 1.
