Page:The Works of William Harvey (part 1 of 2).djvu/346

 one being the brain, the other the cerebellum. All of these are full of perfectly limpid water. In the middle of the blackness of the eye, the pupil is perceived shining like a trans- parent central spark or crystal. I imagine that three of these vesicles being particularly conspicuous, has been the cause of indifferent observers falling into error. For as they had learned from the schoolmen that there was a triple dominion in the animal body, and they believed that these principal parts, the brain, the heart, and the liver, performed the highest functions in the economy, they easily persuaded themselves that these three vesicles were the rudiments and commencements of these parts. Goiter, however, as becomes an experienced anatomist, affirms more truly that whilst he had observed the beak and eyes from the seventh day of incubation, he could yet discover nothing of the viscera.

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 dis- tribution 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 in- terpret his words in this way : although the embryo of the fowl begins to be formed in the albumen, nevertheless it is not nou- rished 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