Page:The Works of William Harvey (part 1 of 2).djvu/555

 surround. The outer of the two common membranes which adheres to the shell is the firmer, that it may take no injury from the shell ; the inner one again is smooth and soft, that it may not hurt the fluids ; in the same way, therefore, as the meninges of the brain protect it from the roughness of the superincumbent skull. The internal membranes, as I have said, include and keep separate their peculiar fluids, whence they are extremely thin, pellucid, and easily torn.

Fabricius ascribes great eminence and dignity to the chalazse, regarding them as the parts whence the chick is formed ; he, however, leaves the spot or cicatricula connected with the mem- brana vitelli without any office whatsoever, looking on it merely as the remains of the peduncle whence the vitellus was detached from the vitellarium in the superior uterus of the hen. In his view the vitellus formerly obtained its nourishment either by this peduncle or the vessels passing through it ; but when de- tached, and no longer nourished by the hen, a simple trace of the former connexion and important function alone remains.

I however am of opinion that the uses of the chalazse are no other than those I have assigned them, namely, that they serve as poles to the microcosm of the egg, and are the association of all the membranes convoluted and twisted together, by which not only are the several fluids kept in their places, but also in their distinct relative positions. But I have absolute assurance that the spot or cicatricula in question is of the very highest im- portance; it is the part in which the calor insitus nestles; where the first spark of the vital principle is kindled ; for the sake of which, in a word, the whole of the rest of the fluids and all the membranes of the egg are contrived. But this has been already insisted on above.

Formerly, indeed, I did think with Fabricius that this cica- tricula was the remains or trace of the detached peduncle ; but I afterwards learned by more accurate observation that this was not the case ; that the peduncle, by which the vitellus hangs, was infixed in no such limited space as we find it in apples and plums, and in such a way as would have given rise to a scar on its separation. This peduncle, in short, expands like a tube from the ovary on towards the vitellus, the horizon of which it embraces in a bipartite semicircle, not otherwise than the tunica conjunctiva embraces the eye ; and this in suchwise