becoming diffused through it, (which is the cause of its spoiling,) so do eggs perish when the yelk spoils, for the lees and the yelk are the more earthy portion in each. Wherefore wine is destroyed by an admixture with its dregs, and an egg by the diffusion of its yelk." 1 And here, too, we may not improperly refer to that passage 2 where he says : " When it thunders, the eggs that are under incubation are spoiled ;" for it must be a likely matter that a membrane so delicate should give way amidst a conflict of the elements. And perhaps it is because thunder is frequent about the dog days that eggs which are rotten have been called cynosura ; so that Columella rightly informs us that " the summer solstice, in the opinion of many, is not a good season for breeding chickens."
This at all events is certain, that eggs are very readily shaken and injured when the fowls are disturbed during incubation, at which time the fluids are liquefied and expanded, and their con- taining membranes are distended and extremely tender.
EXERCISE THE EIGHTEENTH.
The fourth inspection of the egg.
" In the course of the fifth day of incubation," says Aristotle, 3 " the body of the chick is first distinguished, of very small di- mensions indeed, and white ; but the head conspicuous and the eyes extremely prominent, a state in which they afterwards continue long ; for they only grow smaller and shrink at a later period. In the lower portion of the body there is no rudimen- tary member corresponding with what is seen in the upper part. But of the channels which proceed from the heart, one now tends to the investing membrane, the other to the yelk; together they supply the office of an umbilical cord. The chick, therefore, derives its origin from the albumen, but it is afterwards nourished by the yelk, through the umbilicus."
These words of Aristotle appear to subdivide the entire gene- ration of the chick into three stages or periods, viz. : from the
1 Hist. Anim. lib. vi, c. 2. * Ih. lib. viii, c. 5. 3 Ib. lib. vi, c. 3.
