But let us hear the philosopher further: “Of the conduits which lead from the heart, one tends to the investing membrane, another to the yelk, in order to perform the office of umbilicus.” The embryo having now taken shape, these veins do indeed perform the function of the umbilical cord, the ramifications of one of them proceeding to be distributed to the outer tunic which invests the albumen, those of the other running for distribution to the vitellary membrane and its included fluid. Whence it clearly appears that both of these fluids are alike intended for the nourishment of the embryo. And although Aristotle says that “the chick has its commencement in the albumen, and is nourished through the umbilicus by the yelk,” he still does not say that the chick is formed from the albumen. The embryo, in fact, is formed from that clear liquid which we have spoken of under the name of the colliquament, and the whole of what we have called the eye of the egg is contained or included within the albumen. Neither does our author say that the whole and sole nutriment of the embryo reaches it through the umbilicus. My own observations lead me to interpret his words in this way: although the embryo of the fowl begins to be formed in the albumen, nevertheless it is not nourished solely by that, but also by the yelk, to which one of the two umbilical conduits pertains, and from whence it derives nourishment in a more especial manner; for the albumen, according to Aristotle’s opinion, is the more concoct and purer liquid, the yelk the more earthy and solid one, and, therefore, more apt to sustain the chick when it has once attained to greater consistency and strength; and further because, as shall be explained below, the yelk supplies the place of milk, and is the last part that is consumed, a residuary portion, even after the chick is born, and when it is following its mother, being still contained in its abdomen. What has now been stated takes place from the fourth to the tenth day. I have yet to speak of the order and manner in which each of the particulars indicated transpires.