METABOLIC ACTIVITY OF NERVOUS SYSTEM 



373 



We find in table 7 that the percentage of hpoids to soUds (at 

 106 days) is lower in the cerebellum and cerebrum than in the 

 stem or spinal cord as anticipated, and furthermore, in the rats 

 one year old there is a higher content of lipoids than in the 

 one hundred and six days old rats, as can be inferred from the 

 lower percentage of water and of total nitrogen. 



TABLE 7 



Showing the water content, the total nitrogen in solids, lipoids in solids and also 

 nitrogen content in lipoids in different parts of the central nervous system 



It is thus clear that any part of the central nervous system 

 where the myelin, as indicated by the lipoids, is abundant, is 

 poor in the nitrogenous extractives. It appears from this con- 

 clusion, and also from the various relations shown already in the 

 case of the white and gray matter, that the relative content of 

 non-protein nitrogen to the solids, from which the lipoids have 

 been removed, may give a constant value in the several parts of 

 the central nervous system which have been compared. To 

 test this point table 8 was formed, based on the data given in 

 tables 6 and 7. 



As was anticipated, the relation between the protein nitrogen 

 and nitrogen content of extractives is nearly constant. From 

 this we may safely conclude that the lipoids probably have no 

 relation to the nitrogenous organic extractives, and therefore 

 we infer that the organic extractives are an index of the activity 

 of cell substance so far as nitrogenous metabolism is concerned. 



In table 8 we notice one interesting fact, that is the percentage 

 of water is practically constant in the four different parts of the 



