SECT. 9] PROTEIN METABOLISM 1081 



acid. The adult ratio is therefore seen to be attained well before 

 hatching. 



Another nitrogenous excretory product remained to be estimated, 

 namely, ammonia. It was improbable that this would have much 

 effect on the picture of protein metabolism as a whole, but there was 

 a possibility that it might have importance at some special time in 

 embryonic life. The quantitative estimations were done by the Folin 

 method, and led to the values shown graphically in Figs. 321 and 322. 



Table 137. Relations of uric acid and urea. 



Ratio : 



Uric acid/ 



urea milligrams 



per embryo 



Day 4 0-8 



5 0-2 



D 0-2 



7 0-45 



8 1-63 



9 10-80 



10 1 1 -80 



11 i3'io 



12 , 14-31 



13 14-29 



14 15-15 



15 15-73 



16 16-03 



17 15-70 



18 15-77 



19 16-00 



20 16-50 



* Assuming that no other nitrogen compounds are excreted. 



For the increase in ammonia per embryo, the points lie on a well- 

 defined curve, which is practically the same as regards its slope 

 as those previously found for urea and uric acid (Figs. 313 and 328), 

 but it will be seen that the total amounts with which we are now 

 dealing are very much smaller than those of the urea curve, and 

 infinitesimal compared with the amounts of uric acid which the 

 embryo produces. Fig. 322 shows the amounts of ammonia present 

 related to wet and dry weight of embryo. Inspection of this graph 

 shows that the ammonia present in and around 100 gm. of embryo, 

 falls steadily from the beginning of development. Whether the point 

 at the 4th day represents a peak, or a descent from a yet higher 

 value, we do not know. In Fig. 323 the amounts of ammonia, 



69-2 



