78 SHIGEYUKI KOMINE 



fact that some rats show physical exhaustion much quicker than 

 others. It seems to be clear also from the present data that this 

 increase in the amount of non-protein nitre gen in the test brain 

 cannot be the result of inanition, since the period of stimulation 

 is only from one to four hours — mostly one hour — and indeed the 

 increase is often more marked with rats which were stimulated 

 for one hour only. 



We may conclude, then, that as the result of violent fighting 

 the amount of non-protein nitrogen accumulates far in excess of 

 that in the control brain, although the exact cause for such an 

 increase is still to be carefully considered. 



EXPERIMENT SERIES 4 



The experiments so far show clearly that the amount of non- 

 protein nitrogen in the brain increases as the result of stimula- 

 tion, and it was now thought desirable to determine the effect of 

 rest on the content of the metabolites. For this purpose the rats 

 were induced to fight violently for one hour by methods already 

 described. After the lapse of this period, the test rats were placed 

 separately in the usual laboratory cages and kept there with 

 abundant food and water for from twenty-four to forty-two hours. 

 The results of recuperation for these periods are shown in 

 table 4. 



From table 4 it is clear that the amount of non-protein nitrogen 

 in the brain of rats which have rested for twenty-four hours is 

 still significantly higher than those in the control brain. How- 

 ever, in the rats which have rested for forty-two hours the rela- 

 tive amount of non-protein nitrogen is almost the same in both 

 the control and test animals, though the test brains still give a 

 slightly higher value. We might conclude from these data, 

 therefore, that for full recovery to the normal state the rats which 

 have fought violently for one hour require more than forty-two 

 hours' rest. I regret that I cannot extend the observations on 

 resting rats, owing to the limitations of my stay in this country. 



