Page:The Works of William Harvey (part 1 of 2).djvu/545

 action, which is the generation of the chick, the chief cause of this is the semen and the chalazse, these two being the prime cause of the generation of the chick, the semen being the effi- cient cause, the chalaza the matter only." Now according to the opinion of Aristotle, it must be allowed that that which generates is included in the egg ; but Fabricius denies that the semen of the cock is contained in the egg.

Nor does he wander less wide of the mark when he speaks of the chalazae as the matter from which, by the influence of the semen galli, the chick is incorporated. For the chick is not produced either from one or the other, nor yet from both of the chalazse, as we have shown in our history. Neither is the generation of the chick effected by metamorphosis, nor by any new form assumed and division effected in the chalazse, but by epigenesis, in the manner already explained. Nor are the chalazse especially fecundated by the semen of the male bird, but the cicatricula rather, or the part which we have called the eye of the egg, from which, when it enlarges, the colliquament is produced, in and from which, subsequently, the blood, the veins, and the pulsating vesicles proceed, after which the whole body is gradually formed. Moreover, on his own admission, the semen of the cock never enters the uterus of the hen, and yet it fecundates not only the eggs that are already formed, but others that are yet to be produced.

Fabricius refers the albumen and vitellus to the second ac- tion of the egg, which is the nutrition and growth of the chick. " The vitellus and albumen," he says, l " are in quan- tity commensurate with the perfect performance of this action, and with the due development and growth of the chick. The shell and membranes are therefore the safety of the whole of the egg as well as the security of its action. But the veins and arteries which carry nourishment are organs without which the action of the egg, in other words, the growth and nutrition of the chick, would not take place." It is uncertain, how- ever, whether the umbilical vessels of the embryo or the veins and arteries of the mother, whence the egg is increased, are here to be understood. For a like reason the uterus and in- cubation ought to be referred to this last class of actions,

1 Op. cit. p. 48.