SECT. 9] 



PROTEIN METABOLISM 



1095 



® Uric acid nitrogen) Risked 

 O Residual .. / Boyden 

 "P Uric acid n 1^ 

 A Residual - Targonsk. 



9-6. Nitrogen-excretion; Mesonephros, Allantois and Amnios 



The total nitrogen in the allantoic fluid has been measured quanti- 

 tatively by Fiske & Boyden; Sznerovna; Kamei, and Targonski. 

 Kamei's figures are obviously aberrant, but the rest correspond more 

 or less closely, as an inspection of Table 142 indicates well enough. 

 The principal interest of it is the 

 fact, emerging from Fiske & Boy- 

 den's work, that at the earlier 

 stages of development uric acid 

 is by no means the predominat- 

 ing constituent of the nitrogen 

 excretion. The uric acid rises 

 above the rest, however, at the 

 7th day of development. This con- 

 firmed very strikingly my original 

 finding, and the harmony of the 



70 -b 

 60-^ 

 50-1' 

 40 -i 



Days ->■ 5 



t be remembered that Tarffonski 

 '. for 58% of the tt>taJ 

 nitrogen of the ajlojitoic Hqtud 



Fig- 331- 



results is shown in the comparison of Figs. 326 and 331. Targonski's 

 more erratic figures also show the typical cross-over in the importance 

 of uric acid and other nitrogenous molecules as excretory products. 

 What is the residual nitrogen of the early stages ? A balance sheet 

 can be drawn up as follows : 



Table 143. Allantoic liquid {milligrams per embryo). 



From this it is clear that an amount of nitrogen varying from 6 to 

 28 per cent, of that contained in the allantoic liquid is as yet un- 

 accounted for. Examination of the table shows the constant presence 



