246 ON GENERATION. 



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 



