Breaking the shell, and regarding the position of the chick, I found both the remains of the albumen and the two portions of the vitellus (which we have said are divided by the colli- quation induced by the gentle heat), possessing the consis- tency, colour, taste, and other qualities which distinguish the yelks of unincubated eggs similarly boiled. I have, therefore, frequently asked myself how it came to pass that unprolific eggs set under a hen are made to putrefy and become offensive by the same extraneous heat which produces no such effect upon prolific eggs, both of the fluids of which remain sweet and un- changed, although they have an embryo in the midst of them, (and this even containing some small quantity of excrementitious matter within it,) so that did any one eat the yelk of such an egg in the dark, he would not distinguish it from that of a fresh egg which had never been sat upon.
EXERCISE THE TWENTY-THIRD.
Of the exclusion of the chick, or the birth from the egg.
The egg is, as we have said, a kind of exposed uterus, and place in which the embryo is fashioned : for it performs the office of the uterus and enfolds the chick until the due time of its exclusion arrives, when the creature is born perfect. Oviparous animals consequently are not distinguished from viviparous by the circumstance of the one bringing forth their young alive, and the other not doing so ; for the chick not only lives and moves within the egg, but even breathes and chirps whilst there ; and, when it escapes from the shell, enjoys a more perfect ex- istence than the foetus of animals in general. Oviparous and viviparous animals rather differ in their modes of bringing forth ; the uterus or place in which the embryo is formed being within the animal in viviparous tribes, where it is cherished and brought to maturity, whilst in oviparous tribes the uterus, or egg, is exposed or without the animal, which, nevertheless, by sitting on it does not cherish it less truly than if it were still contained within the body.
