Page:The Works of William Harvey (part 1 of 2).djvu/329

 The shell, already less transparent, becomes dingy.

The albumen grows thicker and more viscid, and acquires a straw or yellow colour.

The tunica propria of the vitellus becomes more lax, and appears wrinkled, for it seems that some even of this fluid is dissipated in the course of time.

The chalazse are found in either end of every egg, in the same situation, and having the same consistence whether the egg be recent or stale, fruitful or barren, it does not signify ; by their means a firm connexion is established between the yelk and the white, and the two fluids preserve their relative positions. The chalazse, indeed, are two mutually opposed supports or poles, and hinges of this microcosm ; and are constructed as if made up of numerous coats of the albumen, twisted together at either end into a knotted rope, by which they are attached to the vitellus. And hence it happens that the yelk is separated from the white with difficulty, unless the chalazse are either first di- vided with a knife or torn with the fingers ; this done, the white immediately falls away from the yelk. It is by means of these hinges that the vitellus is both retained in the centre of the egg and preserved of its proper consistence. And they are so connected that the principal part, the cicatricula, to wit, always regards the same region of the egg, or its upper part, and is preserved equidistant from either end. For this spot or cicatricula is observed to be of the same consistence, dimensions, and colour, and in the same situation in the stale as in the new- laid egg. But as soon as the egg, under the influence of the gentle warmth of the incubating hen, or of warmth derived from another source, begins to pullulate, this spot forthwith dilates, and expands like the pupil of the eye, and from thence, as the grand centre of the egg, the latent plastic force breaks forth and germinates. This first commencement of the chick, however, so far as I am aware, has not yet been observed by any one.

On the second day of the incubation, after the egg has been exposed to warmth for twenty-four hours, under the hen, as the cavity in the blunt end has enlarged greatly and descended, so has the internal constitution of the egg also begun to be changed. The yelk, which had hitherto lain in the middle of the albumen, rises towards the blunt end, and its middle, where the cicatricula is situated, is lifted up and applied to the mem-