SECT. 12] GYGLOSES, PHOSPHORUS, SULPHUR 



225 



Kusui 



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experiments of Robertson, that a definite cholesterol-lecithin balance 

 is necessary for the normal functioning of the systems in the living 

 organism. This notion is akin to that contained in Mayer & Schaeffer's 

 cholesterol/lipoid phosphorus ratio, which will presently be discussed. 

 Mueller's findings were later fully confirmed by Dam who found 

 1 2 per cent, of the cholesterol to be esterified at the beginning of de- 

 velopment, but 45 per cent, at the time of hatching, and by Kusui, 

 who could observe no effect of injected adrenalin on the percentage 

 of esters. 



Estimations of the cholesterol in the whole egg were also made by 

 Parke and by Mendel & Leaven- 

 worth — their results are in- 

 cluded in Fig. 389. It was not 

 until 1926 that estimations were 

 made of the cholesterol in the 

 embryonic body, namely by 

 Roffo & Azaretti, using the 

 method of Windaus. Two years 

 later another set of data was 

 obtained by Cahn (see Fig. 379) . 

 The two investigations agree 

 well enough, and the rise is con- 

 tinual, following the growth of 

 the embryo. When related to 

 wet weight, however, Cahn 

 observed a rise, falling off in 

 speed with age, and when re- 

 lated to dry weight, a rise to 

 the mid-point of development, 

 followed by a fall (Fig. 390). Roffo & Azaretti's data show this too. 

 We thus find that 100 gm. of dry weight of embryo contain more 

 cholesterol on the i ith day of development than at any other time. 

 Cahn next calculated the daily increments, and found that they fell 

 on a curve having a peak about the i8th day of development. This 

 curve is plotted in Fig. 382 beside that for daily increments of lipoid 

 phosphorus. Cahn's curve for percentage growth-rate of cholesterol is 

 shown in Fig. 364. 



More recently Kusui has reinvestigated the cholesterol metabolism 

 of the hen's egg, and has made a step forward by showing that except 



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 Ami, All. and White only con- 

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Embryo 



Days- 



Fig- 391- 



