SECT. 9] 



PROTEIN METABOLISM 



1071 



icoag. protein nitrogen (o) \ per 100 gma. 

 luncoag. protein niCrogen(»)J wet egg white 



Oay= -^- 



Fig. 306. 



Vladimirov S(,Schmidtt 



nitrogen in the proteins not so coagulable plus that of all other nitro- 

 genous compounds, on the other. 

 Owing to protein combustion, the 

 former diminishes and the latter 

 rises. Idzumi, on the contrary, 

 obtained the non-protein nitrogen 

 separately from the uncoagulable 

 protein nitrogen, and the free 

 amino nitrogen in addition to that. 

 The free amino nitrogen remains 

 almost constant during develop- 

 ment, thus agreeing with the data 

 already presented, but the total non-protein nitrogen rises owing to 

 the accumulation of protein waste products. 



The protein just referred to, which is not coagulable with acetic 

 acid, is, of course, ovomucoid, and 

 in the Section on carbohydrate meta- 

 bolism an account has been given of 

 our knowledge of the physiology of 

 this compound. Trichloracetic acid 

 was found by Hiller & van Slyke to 

 make a sharp separation between 

 proteins of all kinds and nitrogenous 

 bodies of lower molecular weight. 

 Sakuragi gave for zero hour of de- 

 velopment the values of 1 846 mgm. 

 per cent, of coagulable protein nitro- 

 gen (acetic acid) and 209 mgm. per 

 cent, not so coagulable. Using tri- 

 chloracetic acid, Needham found 

 i960 mgm. per cent, for all protein 

 nitrogen and 90 mgm. per cent, 

 non-protein nitrogen. The increase 

 in the protein nitrogen caught by 

 the trichloracetic acid method over that caught by the simple boiling 

 with acetic acid was thus 114 mgm. per cent. Komori found by 

 alcohol precipitation 480 mgm. of ovomucoid per egg, i.e. 124 mgm. 

 per cent, of ovomucoid nitrogen, which gives close agreement with 

 the extra 1 14 found on using trichloracetic acid as the precipitant. 



Jays 



Fig. 307. 



