SECT. 12] CYCLOSES, PHOSPHORUS, SULPHUR 1215 



of a fall. This fits in with the data for the mouse, as appears from the 

 fact that in Javillier, Allaire & Rousseau's figures for the phosphorus 

 distribution in white mice, the nuclein phosphorus/lipoid phosphorus 

 ratio is above 100 at birth, and then falls. Apparently the nuclein 

 phosphorus never greatly exceeds the lipoid phosphorus. 



So far nothing has been said about the phosphorus in the allantoic 

 liquid of the chick. It has indeed only been estimated by one worker, 

 namely, Targonski. By measuring the total and inorganic phosphorus 

 in the allantoic hquid during the last half of development, he was 

 able to find the percentage of the total allantoic phosphorus existing 

 there in inorganic form, and the ratio : 



Total phosphorus 

 Total nitrogen 



The main results are plotted on Fig. 385. What happens to the in- 

 organic phosphorus in per cent, of the total phosphorus is not very 

 clear; it might be regarded as showing a distinct break at the i6th 

 day, but more probably the relation remains constant. The phos- 

 phorus/nitrogen ratios, however, are very interesting, for both the 

 total phosphorus/total nitrogen and the inorganic phosphorus/total 

 nitrogen decline steadily, the former rather less rapidly than the 

 latter. The phosphorus/nitrogen ratio never reaches that for vitellin, 

 namely, 0-057. ^^ other words, there is always more phosphorus in 

 the allantoic liquid, and sometimes much more, than would result 

 from a simple removal of part of a vitellin molecule (if it was 

 homogeneous) and excretion of the results of its combustion. These 

 problems need much further investigation. 



12-3. Choline in Avian Development 



If now we return to the consideration of Plimmer & Scott's curves 

 for phosphorus distribution throughout the egg, it will be remembered 

 that the ether-soluble phosphorus diminishes greatly, i.e. that the 

 lipoids of the yolk, lecithin and kephalin, are broken down, releasing 

 inorganic phosphorus. The other substances released at the same time 

 are worth consideration. From its formula, one would expect that a 

 good deal of free choline would make its appearance during incuba- 

 tion. The amount of choline in the hen's egg has been studied by 

 Sharpe and by Okada. The former investigator thought that the in- 

 crease in total guanidine during incubation might be due to a decrease 



