248 THE UNFERTILISED EGG AS A [pt. iii 



on the range of individual and racial variations in all the properties 



of eggs. 



The effect of the diet of the hen on the chemical composition of 



the egg has been studied by various workers, notably by Terroine 



& Belin. Except in certain respects, it showed a remarkable fixity 



of composition : 



Table 6. 



Ordinary Corn and potato Hemp seed 

 mixed ration almost ration 



ration free from fats (fatty) 



White in % of total weight ... 56-7 54-3 — 



Yolk in % of total weight ... 31-3 34-0 33-2 



Shell in % of total weight ... 11-4 lo-g — 

 White 



Water % 87-8 87-4 87-4 



Ash% 0-49 — — 



Yolk 



Water % 49-9 50-33 50-99 



Ash% 1-48 — — 



Total nitrogen % ... ... 2-67 — — 



Total fatty acids % 28-4 26-6 2655 



Unsaponifiable fraction % ... 1-85 — 2-08 



Cholesterol % i-i8 1-58 i-ii 



Lecithin P % — 0-425 0-434 



Thus, although the character of the substances stored for the use 

 of the embryo can be varied considerably, as will be seen later, the 

 balance of them cannot. But the question is probably rather com- 

 plicated, for it has been shown by Dam that by feeding hens on a 

 ration rich in cholesterol, the cholesterol content of eggs can be in- 

 creased from 501 to 615 mgm. per cent, of the wet weight or roughly 

 by 22 per cent, of the original value. In another instance the 

 cholesterol rose from 476 to 560 mgm. per cent. This would not be 

 in disagreement with Terroine & Belin's figures, but it would be 

 a very desirable thing to make a detailed study of the limits of 

 variation of all the constituents of the egg, and to find out exactly 

 how different in chemical composition an egg can be from the normal 

 while retaining its hatchability. Klein regards the cholesterol output 

 of the hen in its eggs as showing a synthesis of that substance in the 

 parent body. Leveque & Ponscarme have stated that it was not 

 possible to show any effect on the eggs in eleven breeds of hen by 

 minor variations in the diet; and this was amply confirmed by Gross. 



The ingenious and partially successful attempt of Riddle and 

 Behre & Riddle to make hens preserve their own eggs by feeding 

 them with hexamethylenetetramine, sodium benzoate, and sodium 



