144 K. S. LASHLEY 



grains, respectively, for a 150 pound man, or sixteen and eight 

 times the maximum therapeutic dose. 



The caffeine was administered in doses of 0.50 mgm. and 1.00 

 mgm. These were chosen arbitrarily as corresponding by weight 

 to 4 and 8 grain doses for man. The drugs were adminis- 

 tered each day exactly ten minutes before the beginning of 

 training. This time was chosen as the interval after which the 

 first convulsion appears, following the minimum lethal dose of 

 strychnine. Since Goldscheider and Flatau ('98) have found 

 changes in the cells of the dorsal horn within three minutes after 

 the subcutaneous injection of strychnine the ten minute in- 

 terval seems ample time to assure the full effect of the drug 

 during training. The absence of any easily recognizable effect 

 of the caffeine made it impossible to note its time of action so 

 the same interval between the administration of the drug and 

 the beginning of training was used with it as with strychnine. 



A Luer hypodermic syringe graduated in hundredths cubic 

 centimeters was used for injection. Owing to the small 

 quantity (0.10 cc.) of fluid injected some variation in the size of 

 the dose from day to day was unavoidable. With care, however, 

 it was possible to keep this well within 10 per cent of the total 

 quantity injected. 1 



Method of training. The course of training was as follows. 

 On three consecutive days the rat was confined for fifteen, ten, 

 and five minutes respectively in the feeding compartment of the 

 maze and was given no food except what was eaten there. On 

 the fourth day training was begun. For the first trial the rat 



1 The technique devised for injection has proved so satisfactory that I be- 

 lieve it can be substituted advantageously for that used in many types of work. 

 The usual methods of confining the animals for injection were found to excite 

 them to an extent which threatened to interfere seriously with the experiments 

 and it seemed necessary that the experimenter have both hands free to manipu- 

 late the animals. The hypodermic was therefore fastened by a clamp to project 

 over the edge of a table above which was attached a long lever bearing upon the 

 plunger of the syringe and extending below the table-top so that it could be 

 moved by the experimenter's knee. His hands were thus left free to hold the 

 animal without exciting it, and with careful handling, the animals rarely showed 

 any sensitivity to the injection. With practice it is possible to control the 

 quantity of solution injected by this method to within 0.005 cc. 



