SECT. 12] CYCLOSES, PHOSPHORUS, SULPHUR 



1217 



Nakamura 

 • Total choline in whole egg 



► » r> r> yolk 



'ro " " » embryo 



Sharpe had already published two estimations of this in his pre- 

 liminary note, but Okada's curve amplified them, and demonstrated 

 that, of the choline which is found in the G,gg at the end of incubation, 

 more than two-thirds is uncombined in lecithin. The almost complete 

 disappearance of the combined choline, seen in the work of Sharpe 

 and of Okada, is a striking sidelight on the utilisation of the lipoids 

 of the Ggg by the chick. It has since been confirmed by Fukutomi, 

 but his figures are unfortunately not published. From the data of 

 Sharpe and Okada, the combined choline can be calculated; this 

 corresponds to 386 mgm. per cent, at o day, and 65 mgm. per cent, 

 just before hatching. As there 

 are about 187-8 mgm. per 

 cent, of total phosphorus at 

 the beginning and 62 per cent, 

 of this is lecithin phosphorus 

 (Plimmer & Scott), there must 

 be 115-2 per cent, of lecithin 

 phosphorus, i.e. 2880 mgm. 

 of lecithin, and therefore 390 

 mgm. per cent, of choline — 

 almost exactly what was ob- 

 tained in Sharpe's direct esti- 

 mation. 



Unfortunately, the more 

 recent investigations of Na- 

 kamura have not supported 

 this apparently straightfor- 

 ward story, for, using a simple 

 gravimetric method, in which 



Days-* 5 



Fig. 387. 



the melting-point and other properties of the crystals were verifiable, 

 he obtained results in some opposition to those already described. 

 Fig. 387 shows them. The total choline in the whole Q.gg, according to 

 him, rises by 10 or 15 per cent, from the initial value to a maximum of 

 just over 90 mgm. per egg at the 9th day, after which it rapidly falls oflf, 

 reaching what seems to be a steady level about the i8th day (of about 

 25 mgm. per c^gg). This contrasts with the Sharpe-Okada-Fukutomi 

 results, according to which the whole egg contains some 200 mgm. of 

 total choline before incubation, and some 1 10 mgm.. at the end of it. 

 While in both cases there is a large fall according to Nakamura the 



