ON GENERATION. 453 



where the danger, I ask, of its sinking down, when we see 

 that the egg in incubation is always laid on its side, and there 

 is nothing to fear either for the ascent or the descent of the 

 embryo? It is indubitable, indeed, that not only does the 

 embryo of the chick float in the egg, but that the embryo of 

 every animal during its formation floats in the uterus ; this 

 however takes place amidst the fluid which we have called colli- 

 quament, and neither in the albumen nor vitellus, and we have 

 elsewhere given the reason wherefore this is so. 



" Aristotle informs us," says Fabricius, " that the vitellus 

 rises to the blunt end of the egg when the chick is conceived ; 

 and this because the animal is incorporated from the chalaza, 

 which adheres to the vitellus ; whence the vitellus which was 

 in the middle is drawn towards the upper wider part of the egg, 

 that the chick may be produced where the natural cavity exists, 

 which is so indispensable to its well-being." The chalaza, how- 

 ever, is certainly connected still more intimately with the albu- 

 men than with the yelk. 



My mode of interpreting the ascent in question is this : the 

 spot or cicatricula conspicuous on the membrana vitelli, expands 

 under the influence of the spirituous colliquament engendered 

 within it, and requiring a larger space, it tends towards the 

 blunt end of the egg. The liquefied portion of the vitellus and 

 albumen, diluted in like manner, and concocted and made more 

 spirituous, swims above the remaining crude parts, just as the 

 inferior particles of water in a vessel, when heated, rise from the 

 bottom to the top, a fact which every medical man must have 

 observed when he had chanced to put a measure of thick and 

 turbid urine into a bath of boiling water, in which case the 

 upper part first becomes clear and transparent. Another ex- 

 ample will make this matter still more plain. There is an in- 

 strument familiar to almost everybody, made rather for amuse- 

 ment than any useful purpose, nearly full of water, on the 

 surface of which float a number of hollow glass beads which 

 by their lightness and swimming together support a variety of 

 figures, Cupids with bows and quivers, chariots of the sun, cen- 

 taurs armed, and the like, which would else all sink to the 

 bottom. So also does the eye of the egg, as I have called it, 

 or first colliquament, dilated by the heat of the incubating fowl 



