SECT. 9] PROTEIN METABOLISM 1067 



their values cannot be assessed at its true value from their data 

 alone. As the white is drying up, and the yolk becoming wetter 

 during the first 10 days of incubation, Tomita's figures might be 

 said to be unduly small for the yolk and rather too large for the 

 white, a correction which would exaggerate the difference between 

 them. 



Later still, another Japanese worker, Takahashi, estimated the free 

 bases in the whole egg during development. All were found to rise : 



Milligrams per whole egg 



The general order of magnitude of these figures agrees well with that 

 shown in Fig. 301. 



Aggazzotti, who was working at much the same time as Tomita, 

 took the changing water-content of the yolk and white into con- 

 sideration. Aggazzotti precipitated the proteins in the yolk and 

 white by the Costantino acid sublimate technique, estimated the 

 total and the amino nitrogen in the filtrate, and then, hydrolysing 

 the proteins, estimated their total nitrogen, their amino nitrogen and 

 their ammonia. The results he obtained are shown in Figs. 302 and 

 303. As regards the white, there was no change at all in the total 

 protein nitrogen, or in the bound amino-acid nitrogen, though the 

 ammonia of the proteins diminished by more than 50 per cent. The 

 significance of this fall in the protein ammonia is not at all clear. 

 Matters took very much the same course in the yolk, where the 

 protein nitrogen and the bound amino-acid nitrogen remained con- 

 stant, while the bound ammonia rose a little before falling. The free 

 amino nitrogen, plotted in Fig. 304, showed practically no change 

 when related to dry weight in the yolk, but rose and fell in the white 

 with a maximum at the 8th day. However, when the free amino 

 nitrogen was compared with the total free nitrogen, so that a measure 

 was obtained of the extent to which the free amino-acids accounted for 

 the non-protein nitrogen at any moment, the curves of Fig. 305 were 

 obtained. From them it appears that there is a maximum of free 



