70 SHIGEYUKI KOMINE 



eliminating as much as possible the factor of fear from the con- 

 trol rats. The rats were usually fed with a mixture of 'Uneeda 

 biscuit' and condensed milk, at about 9 a.m. In making the 

 tests two male rats were put into a box which was constructed 

 in the following manner: A wooden box about 11 inches long, 10 

 inches wide and 8 inches high was made, in the bottom of which 

 numerous nails were placed with their tips just exposed on the 

 inner surface of the bottom. These nails were connected by- 

 means of a copper wire and the ends of these wires were in turn 

 connected with a battery, so that an electric current could pass 

 through them. The rats standing in this box were stimulated for 

 a period of three seconds in every two minutes by the passage 

 of a current. The rats began to fight immediately or shortly 

 after the electrical shock was given, as if one rat held the 

 other responsibile for the shock received. Sometimes the rats 

 refuse to fight, and in such cases a light pricking of the tail with 

 a sharp needle always provokes fight almost at once. When once 

 started, the rats continued fighting under the stimulus of the 

 electrical shock alone. Usually the two test rats were taken from 

 different litters, because the rats which belong to the same litter 

 and are accustomed to living in the same cage do not normally 

 fight with each other. 



When the rats were brought from the rat house, I put those 

 of the same litter in two separate boxes, one control rat and 

 one test rat in one box, another control and test rat in the other 

 box. Rats of more than 120 days of age were chosen, because 

 Hatai ('17) found that the amount of non-protein nitrogen shows 

 very slight age alteration after the rats pass this age, while on 

 the other hand the rats which are younger do not fight vigor- 

 ously. Males only were used. 



The rats may continue fighting vigorously for several hours. 

 In this operation both rats stand on their hind feet and push 

 each other with their front paws, holding their bodies erect and 

 straight and their mouths almost touching each other. Every 

 time a shock passes both squeak and each pushes the other 

 strongly and they may even bite one another. In some cases 

 the rats continue this performance for more than six hours, while 



