80 SHIGEYTJKI KOMINE 



DISCUSSION 



From the data presented it seems clear that as the result of 

 severe fighting the amount of non-protein nitrogen increases con- 

 siderably in the brain. The interpretation of this phenomenon 

 is difficult. In association with violent fighting there is more or 

 less physical exercise, which necessarily accompanies fighting, 

 and we should anticipate an effect of fatigue and whatever 

 changes such fatigue may produce on the brain. Because great 

 emotional disturbance is necessarily associated in this case with 

 marked bodily activity, the greater amount of non-protein nitro- 

 gen found in the brain in the present experiment might be con- 

 sidered a result of abnormal physiological activity of various 

 organs and tissues, besides that of the nervo'us system itself. 



„The sources of non-protein nitrogen in the central nervous sys- 

 tem are two; one is that of the metabolites transported to the 

 brain by means of the blood, and the second is the production 

 of metabolites by the nervous tissue itself. It is, however, im- 

 possible to determine from the present experiments alone which 

 of these sources should be held more largely responsible for the 

 greater accumulation of the metabolites in the brain. It is, how- 

 ever, true that the greater activity of the muscles and organs 

 during severe fighting must increase the amount of metabolites 

 in general, and at the same time we are also justified in conclud- 

 ing that the brain tissue itself must increase in its activity. This 

 latter conclusion follows from the investigations of Hodge ('92), 

 which showed that conspicuous structural alterations of the 

 spinal ganglion cells follow the direct electrical stimulation of 

 peripheral nerves. Hodge further demonstrated that the cells of 

 spinal ganglia of English sparrows, of the cerebrum of pigeons, 

 and cerebellum of swallows and antennal lobes of bees obtained 

 at the end of the day, that is, after a period of activity, show 

 structural changes as compared with those obtained at the be- 

 ginning of the day, or after a night of rest. 



Similar observations were made subsequently by several ob- 

 servers, and we may mention here the work of Mann ('95) on 

 the motor cells of the spinal cord and cells of the retina as one 

 illustration. 



