364 



S. HATAI 



TABLE 1 

 Showing the content of total nitrogen as well as non-protein nitrogen in the entire 



diminishes mth advancing age as does the total nitrogen. How- 

 ever the rate of reduction is plainly more rapid in the non- 

 protein nitrogen than in the total nitrogen. Indeed the brain 

 at 382 days of age gives a non-protein nitrogen value which is 

 only one half of that at one day. If non-protein nitrogen were 

 closely related to the total nitrogen content we might anticipate 

 a parallel fall of their value at given ages. This, as the table 

 shows, is not the case. It is therefore possible that the greater 

 reduction of non-protein nitrogen compared with the total 

 nitrogen might be due to an accumulation of the myelin nitrogen 

 which in turn may not be closely related to the formation of the 

 non-protein nitrogen. Therefore the two sets of data might 

 show changes which are more nearly parallel if we should cal- 

 culate the total nitrogen for the solids from which the myelin 

 has been removed. This test can not be made at this moment 

 on account of a lack of necessary data. It will be seen later how- 

 ever that this supposition that the non-protein nitrogen is quan- 

 titatively related to the non-lipoid fraction in the brain is well 

 supported. 



