328 ON GENERATION. 



frequently discordant. The first difficulty is in reference to the 

 matter and nourishment of the chick. Hippocrates, 1 Anaxa- 

 goras, Alcmaeon, Menander, and the ancient philosophers, all 

 thought that the chick was engendered from the vitellus, and 

 was nourished by the albumen. Aristotle, 2 however, and 

 after him, Pliny, 3 maintained, on the contrary, that the chick 

 was incorporated from the albumen, and nourished by the 

 vitellus. But Fabricius himself, will have it that neither the 

 white nor yelk forms the matter of the chick ; he strives to com- 

 bat both of the preceding opinions, and teaches that the white 

 and the yellow alike do no more than nourish the chick. 

 One of his arguments, amongst a great number of others which 

 I think are less to be acquiesced in, appears to me to have 

 some force. The branches of the umbilical vessels, he says, 

 through which the embryo undoubtedly imbibes its nourish- 

 ment, are distributed to the albumen and the vitellus alike, and 

 both of these fluids diminish as the chick grows. And it is 

 on this ground, that Fabricius in confirmation of his opinion, 

 says 4 : " Of the bodies constituting the egg, and adapted to 

 forward the generation of the chick, there are only three, the 

 albumen, the vitellus, and the chalazse ; now the albumen and 

 vitellus are the nourishment of the chick ; so that the chalazse 

 alone remain as matter from which it can be produced." 



Nevertheless, that the excellent Fabricius is in error here, 

 we have demonstrated above in our history. For after the 

 chick is already almost perfected, and its head and its eyes are 

 distinctly visible, the chalazse can readily be found entire, far 

 from the embryo, and pushed from the apices towards the sides : 

 the office of these bodies, as Fabricius himself admits, is that 

 of ligaments, and to preserve the vitellus in its proper position 

 within the albumen. Nor is that true, which Fabricius adds 

 in confirmation of his opinion, namely, that the chalazae are 

 situated in the direction of the blunt part of the egg. For after 

 even a single day's incubation, the relative positions of the fluids 

 of the egg are changed, the yelk being drawn upwards, and the 

 chalazse on either hand removed, as we have already had occa- 

 sion to say. 



' Lib. de Nat. Pueri. 



9 Hist. Anim. lib. vi, cap. 3, et de Gen. Anim. lib. iii, cap. 1 & 2. 



* Lib. x, cap. 53. 4 Op. cit. p. 34. 



