1222 METABOLISM OF LIPOIDS, STEROLS, [pt. iii 



extracted it for 12 days with ether in a Soxhlet. The cholesterol in 

 the unsaponifiable fraction was estimated gravimetrically as cholesterol 

 benzoate. They found that no increase took place during develop- 

 ment, the cholesterol accounting for 382-7 mgm. per cent, of the wet 

 weight of the egg, and for 369-3 mgm. per cent, of the wet weight 

 of the hatched chicks, or 317-2 mgm. per cent, expressed in terms 

 of the original weight of the eggs. At first sight it would seem as if 

 there had occurred a loss of cholesterol from the egg, but Ellis & 

 Gardner pointed out that the difference between the average per- 

 centage in eggs and in chicks, i.e. 66 mgm., was of much the same 

 order of magnitude as the average deviation from the mean in the 

 two cases, i.e. 57 mgm. for the eggs and 75 mgm. for the chicks. 

 So, as they only analysed 8 eggs and 8 chicks, and as they were not 

 very confident in their method, they preferred to conclude that in all 

 probability neither loss nor gain took place during the incubation 

 of the egg. In another experiment in which 6 eggs and 6 chicks 

 were analysed together, 489 mgm. per cent, were obtained in the 

 former case, and 467 mgm. per cent, in the latter. 



This result substantiated the view held in all their investigations 

 by Ellis & Gardner, namely, that cholesterol cannot be synthesised 

 by the animal body. However, Channon and Dam demonstrated 

 some years later that the reverse proposition is true for the chick 

 after hatching, and it was not long before Thannhauser & Schaber, 

 using Windaus' method, reported an increase of total cholesterol 

 during the incubation period. Their data were as follows: 



Days 



Change 



Thus the free cholesterol decreased by 26 per cent, of the initial 

 value, the combined cholesterol increased by 128 per cent, of the 

 initial value, and the total cholesterol, thus partially compensated, 

 increased by 10-7 per cent, of its initial value. We see here clearly 

 that production of cholesterol esters observed histochemically by 

 Hanes. Roffo & Azaretti, the next workers on the sterols of the 

 egg, found no marked change in the cholesterol content of the whole 

 egg before and after incubation, there being 219 mgm. per egg at 



