ON GENERATION. 307 



a white. For the same faculty that presides over the formation 

 of the egg in general, presides over the constitution of each of 

 its parts in particular. Neither is it altogether true that the 

 yelk is first formed and the albumen added to it afterwards; for 

 what is seen in the ovary is not the vitellus of the egg, but rather 

 a compound containing the two liquids mingled together. It 

 has the colour of the vitellus, indeed, but in point of consistence 

 it is more like the albumen; and when boiled hard it is not 

 friable like the proper yelk, but, like the white, is concreted, 

 jelly-like, and seen to be composed of thin lamellae; and it 

 has a kind of white papula, or spot, in the middle. 



Aristotle seems to derive this separation from the dissimilar 

 nature of the yelk and white; for he says, 1 as we have already 

 stated, that if a number of eggs be thrown into a pan and 

 boiled, in such wise that the heat shall not be quicker than the 

 separation of the eggs, (citatior quam ovorum distinctio,) the 

 same thing will take place in the mass of eggs which occurs in 

 the individual egg : the whole of the yelks will set in the middle, 

 the whites round about them. 



This I have myself frequently found to be true on making 

 the trial, and it is open to any one to repeat the experiment ; 

 let him only beat yelks and whites together, put the mixture 

 into a dutch oven, or between two plates over the fire, and 

 having added some butter, cause it to set slowly into a cake, 

 he will find the albumen covering over the yelks situated at 

 the bottom. 



EXERCISE THE THIRTY-EIGHTH. 



Of what the cock and hen severally contribute to the production 

 of the egg. 



Both cock and hen are to be reputed parents of the chick ; 

 for both are necessary principles of an egg, and we have 

 proved both to be alike its efficient : the hen fashions the egg, 

 the cock makes it fertile. Both, consequently, are instruments 



1 Fabricius, op. cit. p. 12. 



