SECT. 9] PROTEIN METABOLISM 1113 



where the composition of the lost nitrogen is shown. Here again is a 

 correspondence with Plimmer & Lowndes. The ammonia and humin 

 nitrogen also rise. 



In this connection reference must be made to the paper of Tangl & 

 Farkas on the trout egg, which has been already discussed on 

 p. 955. In the course of their calorimetric study they obtained the 

 following figures : 



Milligrams per lOO individuals 



Undeveloped eggs Hatched fry Gain or loss 

 Wet weight ... ... 8850 8330 —520 



Dry weight ... ... 2990 2915 —75 



Fatty acids ... ... 639 663 +24 



Nitrogen 359 357 -2 



Carbon ... ... 1672 1635 -37 



Tangl & Farkas did not regard the loss of nitrogen as significant, 

 but there was certainly a gain in fatty acids. This phenomenon will 

 receive some consideration in Section ii-8; all that need be said 

 here is that this demonstration of the fixity of the total nitrogen does 

 not imply that no protein had been catabolised, as the urea or am- 

 monia would be included in the total nitrogen. 



Gortner determined the phenol content of the phosphotungstic 

 filtrate, and observed a loss of 29 per cent, throughout the whole 

 period, principally after hatching, which may or may not have been 

 tyrosine. As stated above, the 400 embryos lose throughout the 

 whole period 191 1 mgm., of which 1190 mgm. is protein, so Gortner 

 concluded that 62-7 per cent, of the total food-stuflf" catabolised 

 must come from the proteins, and 37-2 per cent, from other substances. 

 (See Table 126.) 



Pearse has also studied the eggs of fresh- water fishes, particularly 

 the brook-trout. In his paper of 1925 he stated that the nitrogen 

 diminishes from the ist day of development till after the end of the 

 yolk-sac period, but the published details are meagre. Hayes states 

 that there is no diminution of the total nitrogen before hatching in the 

 egg of the Atlantic salmon {Salmo salar) but that there is in that of the 

 lumpsucker {Cyclopterus lumpus). Levene's experiments on the cod's 

 egg [Gadus morrhua) were not unlike those of Gortner on the trout. 

 The following table shows that the eggs as a whole lose water as 

 they develop, and that there is a distinct loss of nitrogen, although 

 the figures are erratic. The data for basic and non-basic nitrogen and 

 protein nitrogen are so uneven, rising and falling in leaps between 



