[o68 



PROTEIN METABOLISM 



[PT. Ill 



amino-acids (expressed in this way) in the yolk at about the 3rd day 

 and in the white at about the 7th day. As will appear presently, this 

 result fits in well enough with other data obtained on the embryo 

 itself. As regards the wet weight of the white, Aggazzotti was in agree- 

 ment with Tomita in finding an increase of free amino-acids so 

 related, in the case of the yolk precisely the opposite held good. 



The main conclusion which can be drawn from the work of Tomita 

 and Aggazzotti is that the changes in amino-acid concentration in 

 the yolk and white are rather minute. There was certainly no a priori 

 reason for expecting big changes, for the transfer of amino-acid mole- 



Aggazzotbifyolk) 

 e Total protein nitrogen 

 e Bound amino-acid nitrogen 

 © » ammonia nibroqen 



K 





Days 



Days ■*• 5 



Fig. 302. 



Fig. 303- 



cules from egg to embryo might vary very greatly in intensity without 

 involving a difference in absolute amount or concentration of the 

 intermediary substances. 



Later, Vladimirov & Schmidtt precipitated the proteins of the egg- 

 white during development by the Fischer-Bang uranium acetate 

 method, and by doing Kjeldahl estimations on the precipitate and the 

 filtrate obtained figures for the protein and non-protein nitrogen. 

 The former increased steadily as the water-content of the white 

 diminished; the latter also increased steadily, so that the ratio pro- 

 tein nitrogen/non-protein nitrogen was constant. Both are plotted 

 beside Tomita's results in Fig. 301, with which they agree. Aggaz- 

 zotti's results are much higher all through. Thus all observers agree 



