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.
