io62 



PROTEIN METABOLISM 



[PT. in 



probably real. This again is not in agreement with the work of 

 Plimmer & Lowndes; Sendju, and Russo. 



The fact of the matter is that the estimation methods available are 

 insuflficiently delicate to show up clearly the slight changes which 

 occur in these amino-acid distributions. One reflection, at any rate, 

 may be made, namely that the raw material of the embryo is not 

 very different from the embryo itself: half the di-amino-acids, for 

 instance, do not have to be made into mono-amino-acids. Would 



Lysine 



500 



© Embryo 

 O White 

 • YotW 

 ® Whole egg 



Nitrogen not preci pi table with 



phosphotungstic acid 



(monoamino acids) 



Days -+5 



5 20 Days ^5 



Fig. 298. 



this be equally true of an embryo which did not have to suppress its 

 protein catabolism, as is the case with terrestrial animals? Parallel 

 studies with aquatic eggs should certainly be undertaken. And one 

 also wonders, if the hen's egg economises its amino-acids to such an 

 extent, whether they ever go down to individual simplicity at all, or 

 whether they do not rather enter the embryo in the form of proteose 

 bundles. 



Sendju did not give his amino-acid results in terms of the weight 

 of the embryo, but they have been calculated in this way, and 

 are shown in Fig. 299. Sagara has also made some estimations of 

 the arginine, histidine and lysine content of the embryo, but they 



