Parisanus, falling upon these regions, is grossly mistaken when he speaks of “a honey-coloured, a white, a gray, and another white circle;” and says that “the fœtus is formed from the white middle point” (which, indeed, appears in these regions), and that “this is the semen of the cock.” That he may exalt himself on a more notable subtlety he continues: “Before any redness is apparent in the body of the fœtus, two minute vesicles present themselves in it; in the beginning, however, neither of them is tinged with red;” one of these he would have us receive as the heart, the other as the liver. But in truth there is neither any vesicle present sooner than the redness of the blood is disclosed; nor does the embryo ever suddenly become red in the course of the first days of its existence; nor yet does any of these vesicles present us with a trace of the liver. Both of them belong, in fact, to the heart, prefiguring its ventricles and auricles, and palpitating, as we shall afterwards show, they respond reciprocally by their systoles and diastoles. Aristotle[175] 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. Coiter 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 fœtuses of every animal. Whilst they float in it they are safe from succussion 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.