SECT. lo] THE NITROGENOUS EXTRACTIVES 1161 



The subject was gone into in more detail by Sendju, who estimated 

 the creatine and creatinine in yolk, white and embryo. As Fig. 355 

 shows, the preformed creatinine never exceeds i mg. in the embryo, 

 while the creatine rises to about 8 mg. The amounts contained in 

 the yolk and white are at all times negligible, and it is evident that 

 a \dgorous synthesis must be proceeding. 



The allantoic liquid, as has already been stated, contains creatine 

 and creatinine. The concentrations of these substances rise steadily 

 during development, as Fig. 356, plotted from the data of Fiske & 

 Boyden and of Kamei, demonstrates. 



As regards the origin of creatine and creatinine in the egg, nothing 



9 )0 11 1? 13 14 15 16 17 18 19 20 21 22 23da_>'S 

 Fig. 357- 



is known. The only attempt which has been made to find out is 

 that of Burns, who in 1916 estimated the total guanidine in the hen's 

 ^gg throughout incubation. The guanidine molecule is very resistant 

 to oxidation, and Kutscher found that if a soluble protein is treated 

 repeatedly with boiUng calcium permanganate, a mixture of oxida- 

 tion products is obtained from which much can be driven off as 

 aldehydes, ammonia, carbon dioxide, etc., and from which the 

 guanidine can be precipitated with picric acid. This was the method 

 employed by Burns, who operated on whole eggs including every- 

 thing except the shell. Fig. 357, taken from his paper, shows the 

 grams of guanidine picrate found in per cent, of the egg-contents. 

 There is clearly a steady increase in total guanidine picrate from 

 0*3 to 2-8 per cent, at the 12th day, after which there is a falling 



74-2 



