242 ON GENERATION. 



heart, is no longer seen to move externally, but to be covered 

 over and concealed; still its two meatus venosi are perceived 

 more distinctly than before, one of them being, further, larger 

 than the other. " But our learned author was mistaken here; for 

 this familiar divinity, the heart, enters into his mansion and shuts 

 himself up in its inmost recesses a long time afterwards, and when 

 the house is almost completely built. Aldrovandus also errs when 

 he says, " by the vis insita of the veins, the remaining portion 

 of the albumen acquires a straw colour," for this colour is ob- 

 served in the thicker albumen of every spoilt egg, and it goes 

 on increasing in depth from day to day as the egg grows staler, 

 and this without any influence of the veins, the thinner portion 

 only being dissipated. 



But the embryo enlarging, as we say below, and the ramifi- 

 cations of the meatus venosi extending far and wide to the al- 

 bumen and vitellus, portions of both of these fluids become 

 liquefied, not indeed in the way Aldrovandus will have it, from 

 some vis insita in the vessels, but from the heat of the blood 

 which they contain. For into whatsoever part of either fluid 

 the vessels in question extend, straightway liquefaction ap- 

 pears in their vicinity; and it is on this account that the 

 yelk about this epoch appears double : its superior portion, 

 which is in juxtaposition with the blunt end of the egg, has 

 already become more diffluent than the rest, and appears like 

 melted yellow wax in contrast with the other colder firmer por- 

 tion; like bodies in general in a state of fusion, it also occupies 

 a larger space. Now this superior portion, liquefied by the 

 genial heat, is separated from the other liquids of the egg, but 

 particularly the albumen, by a tunica propria of extreme tenuity. 

 It therefore happens that if this most delicate, fragile, and in- 

 visible membrane be torn, immediately there ensues an admix- 

 ture and confusion of the albumen and vitellus, by which every- 

 thing is obscured. And such an accident is a frequent cause 

 of failure in the reproductive power, (for the different fluids in 

 question are possessed of opposite natures,) according to 

 Aristotle, 1 in the place already so frequently referred to : " Eggs 

 are spoiled and become addled in warm weather especially, and 

 with good reason; for as wine grows sour in hot weather, the lees 



1 De Gener. Anim. lib. iii, c. 2. 



