72 SHIGEYUKI KOMINE 



conventional mark made by some other member of the laboratory 

 and thus the non-protein nitrogen determinations were conducted 

 in entire ignorance as to which flask belonged to the control or 

 which to the test series, thus avoiding any personal bias in the 

 determinations. 



EXPERIMENT SERIES 1 



These experiments have been made to see whether or not the 

 amount of non-protein nitrogen in the brain is changed as the 

 result of stimulation (fghting). Altogether six control and six 

 test animals were used. The period of stimulation extended 

 from ten to twenty-four hours. The rats did not fight at all 

 in two cases and only slightly in one. Tn no instance was the 

 method of pricking with a needle applied to induce fghting. 

 During the experimental period both the control and test ani- 

 mals were not fed except with water. The results are shown in 

 table 1. 



As will be seen from table 1, the relative amount of non-protein 

 nitrogen (per 100 grams) in the brain of the test rat is signifi- 

 cantly greater than those given by the control rat. The amount 

 of difference is greatest in the rats which had been stimulated 

 for the longest period, but this may be mere coincidence, since 

 the other two cases do not follow in this relation. The present 

 results bring out at least two points. Since these rats were not 

 fed during the period of stimulation, it is conceivable that the 

 electrical shocks, although they did not induce actual fighting, 

 might nevertheless through periodic irritation accelerate meta- 

 bolic activity as compared with the rats which were not stimu- 

 lated, and thus produce a form of mild inanition. It has been 

 already found in my previous studies ('19) that during inanition 

 (represented by the later part of the twenty-four-hour period) 

 the non-protein nitrogen content of the brain shows some in- 

 crease. It will be seen, however, from the later experiments that 

 this increase in the non-protein nitrogen may be mainly due to 

 stimulation, though inanition may also contribute to it. 



We might also assume that this increase of non-protein nitro- 

 gen in the test brain is due to the increased metabolic activity of 



