METABOLIC ACTIVITY OF NERVOUS SYSTEM 405 



• 



not extensive enough (only up to seven hours after feeding), 

 and thus a periodic variation in the non-protein nitrogen con- 

 tent, such as I have found in the brain, did not appear. Mitch- 

 ell's observations, however, show clearly that the amount of 

 amino acids and urea, as well as ammonia, are regularly higher 

 in the fed than in the fasting animal, and furthermore, these 

 fed rats show rapid increase in the non-protein nitrogen during 

 the first five hours, and then slight decrease at seven hours, not 

 only in the entire body, but in such organs as the kidneys, liver, 

 and muscles. Despite the somewhat greater irregularities of 

 the data given by Mitchell, the increase in the content of these 

 simpler nitrogenous bodies during active protein digestion is 

 well indicated. 



RELATION OF THE NON-PROTEIN NITROGEN TO THE TOTAL 



NITROGEN 



From the amount of non-protein nitrogen in the four divi- 

 sions of the central nervous system of the rats, Hatai ('17) came 

 to the following conclusions. "Although the amount of nitrogen 

 given by the non-proteins — the amino acids, the urea and 

 ammonia — in relation to the solids is higher in the cerebellum 

 and cerebrum than either the stem or the spinal cord, these 

 nitrogen values become constant in all the four parts when they 

 are computed in relation to the protein nitrogen. This is inter- 

 preted to mean that the nitrogenous organic extractives are 

 intimatelj^ related with the active cell substance, and not at all 

 with the lipoid substance." 



Following the statement of Hatai, it was thought desirable to 

 find the relation which exists between the amount of non-protein 

 nitrogen in the brain and the amount of total nitrogen, because 

 by this means we can find a much closer relation between the 

 active cell substance which is expressed in the present instance 

 in terms of total nitrogen and metabolic products, owing to the 

 elimination of myelin substance mainly. 



The data for this determination are given in table 1, and I 

 shall now discuss this observation as it appears in the graph 

 given in chart 2. 



