. Chemical embryology. Embryology. 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
. Chemical embryology. Embryology. 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, 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 , 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 som
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Keywords: ., bookcentury1900, bookpublishernewyorkthem, booksubjectembryology
