Page:The Works of William Harvey (part 1 of 2).djvu/496

 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