396 ON GENERATION. 



chyle by which all animals are nourished is brought by the 

 mesenteric veins from the intestines ; nor is there occasion to 

 look for any new passage by the lacteal vessels, to wit or 

 any route in adult animals other than that which we discover in 

 the egg and chick. But we shall recur more fully in another 

 place to the inconveniences of such an opinion as that re- 

 ferred to. 



Lastly, from the structure of the umbilical vessels of the 

 chick in ovo, some of which as stated in the history are veins, 

 others arteries, it is legitimate to conclude that there is here a 

 circular motion of the blood, such as we have already demon- 

 strated in the animal body, in our book on the Motion of the 

 Blood, and this for the sake of the nutrition and growth of the 

 embryo, and because the umbilical veins are distributed to 

 either fluid of the egg, that they may thence bring nutriment 

 to the chick, and the arteries accompany the veins, that by 

 their affluxive heat the alimentary matter may be duly con- 

 cocted, liquefied, and made fit to answer the ends of nutrition. 



And hence it happens that wherever veins and here I 

 would have it understood that both arteries and veins are in- 

 tended make their way into the albumen or vitellus, there 

 these fluids look liquefied and different from the -rest. For 

 as soon as the branches of the veins shoot forth, the upper 

 portion of the albumen in which they are implanted passing 

 into colliquament, becomes transparent, whilst the lower por- 

 tion, continuing thick and compact, is pushed into the inferior 

 angle of the egg. In like manner a separation of the vitellus, 

 as it seems into two portions, makes its appearance, the one 

 being superior, and the other inferior, and these do not differ 

 less from one another in character than melted differs from solid 

 wax; now this division corresponds to the two parts which se- 

 verally receive or do not receive blood-vessels. 



Hence are we farther made more certain as to the com- 

 mencement of animal generation and the prime inherent prin- 

 ciple of the egg. For it is assuredly known that the cicatricula 

 or spot on the yelk is the chief point in the egg, that to which 

 all the rest are subordinate, and to which, if to any one thing 

 more than another, is to be referred the cause, whatever it be, 

 of fecundity in the egg : certain it is that the generation of 

 the embryo is begun within its precincts. Wherefore, as we have 



