Aristotle 1 appears to have known this dissolved fluid, when he says : " A membrane, too, marked with sanguineous fibres, surrounds the white fluid at this time (the third day), arising from those orifices of the veins." Now the philosopher can neither be supposed by the words " white fluid," to refer to the albumen at large, because at this period the membrane of the white is not yet covered with veins; it is only the membrane of the dissolved fluid which appears with a few branches of veins distributed over it here and there. And because he says : "this membrane, too," as if he understood another than those which he had spoken of as investing the albumen and the yelk before incubation, and designated this one as first arising after the third day, and from the orifices of the veins.
Goiter seems also to have known of this dissolved fluid ; he says : " A certain portion of the albumen acquiring a white colour, another becoming thicker." The fluid in question is surrounded with its proper membrane, and is distinct and separate from the rest of the albumen before there is any appearance of blood. We shall have occasion, by and by, to speak of the singular importance of this fluid to the foetuses of every animal. Whilst they float in it they are safe from suc- cussion and contusion, and other external injury of every kind; and they moreover are nourished by it. I once showed to their serene majesties the king and queen, an embryo, the size of a French-bean, which had been taken from the uterus of a doe ; all its membranes were entire, and from its genital organs we could readily tell that it was a male. It was, in truth, a most agreeable natural spectacle ; the embryo perfect and elegant, floating in this pure, transparent, and crystalline fluid, invested with its pellucid tunica propria, as if in a glass vessel of the greatest purity, of the size of a pigeon's egg.
EXERCISE THE SEVENTEENTH.
The third inspection of the egg.
Having seen the second process or preparation of the egg, towards the production of the embryo which presents itself in 1 Hist. Anim. lib. vi, cap. 3.
