SECT. 12] CYCLOSES, PHOSPHORUS, SULPHUR 1221 



which gave all the reactions of cholesterol esters. Hanes suggested 

 that finally the yolk-sac, Hke the Hver, takes part in the decompo- 

 sition of the lecithin molecule. Finally, he recalled that Windaus 

 had reported the presence of a great deal of esterified cholesterol 

 in areas of pathological calcification, such as atherosclerotic aortas. 

 He mentioned that in examining the livers of foetal dogs and of 

 new-born puppies he had found a large quantity of anisotropic 

 droplets. On the other hand, he failed to find any in the liver of the 

 foetal pig (stage of development not stated) . 



Apparently Hanes was unaware of some work of Valentin published 

 as early as 1871. Valentin investigated the doubly refracting droplets 

 in chick embryos, and stated that none of the tissues of the 3rd, 4th, 

 5th or 6th day embryos showed them, but that on the 7th day a very 

 few appeared. He obtained comparable results in a study of the 

 embryonic liver of the frog. Chalatov also had reported anisotropic 

 globules in liver cells of rabbits fed with egg-yolk for 5 months. 

 After Hanes' report, work was continued on much the same lines by 

 Yamaguchi, who examined the livers of the foetuses of man, the rabbit, 

 dog, guinea-pig, bat, toad, snake and salmon. In the two latter cases 

 no cholesterol esters ever appeared as in all the others. In the human 

 foetal liver, the esters appeared about the end of the ist month, 

 and increased in amount — as far as histochemical work could show — 

 until the beginning of the 5th month, after which they disappeared. 



Chemical estimations of free and combined cholesterol in the hen's 

 egg during development have, generally speaking, confirmed the 

 views of Hanes, and indeed widely extended them. Its absorption 

 from the yolk was studied by Idzumi, who simply estimated the 

 amount of unsaponifiable substance in the petrol-ether extract. It 

 is impossible to decide what his data mean, for he obtained much 

 more total unsaponifiable substance when he estimated the embryo 

 and the remainder separately than when he estimated the whole egg. 

 The work of Mueller was on a different level, but, before considering it, 

 it will be convenient to discuss the question of whether cholesterol is 

 synthesised at all by the developing chick embryo. To settle this it was 

 only necessary to estimate the total cholesterol present at the beginning 

 of development, and to compare it with the total cholesterol present at 

 the end. The first workers to do this were Ellis & Gardner in 1908. 

 They pounded up the eggs and embryos in mortars with plaster of 

 paris, and allowed the mass to set, after which they powdered it, and 



