148 K. S. LASHLEY 



of day during which the different groups were trained. Hub- 

 bert has shown, further, that the rate of learning is not influ- 

 enced by the time of training. (5) Seasonal variations. No 

 seasonal variation in the learning ability of the rat has been 

 demonstrated, but to control possible variations the experiments 

 were condensed into the shortest possible time and correspond- 

 ing members of all groups were trained at the same time. (6) 

 Differences of weight. Where differences in the weight of sib- 

 lings existed their distribution to the different groups was left 

 to chance. The actual differences in the average weights of the 

 groups were very slight. 



Individual differences in the rats other than those noted 

 above were beyond control and may have played some part in 

 determining the results obtained. A further argument, how- 

 ever, in favor of the validity of the differences found between 

 the different groups as indices of the effects of the drugs is the 

 internal agreement between the results of the different experi- 

 ments which will be considered later. 



In the training of animals the personal equation of the ex- 

 perimenter may be influential in deciding the rate of learning. 

 I have sometimes thought that my methods of handling the 

 animals influenced their behavior in the maze, but I have not 

 been able to get any definite evidence of such an influence. 

 Throughout the experiments I made every effort to keep the 

 treatment of all the animals the same and to detect any in- 

 voluntary favoring of one group or another. Furthermore, 

 the most significant check upon the personal equation is the 

 fact that the results obtained were wholly unexpected and by 

 no means agreeable to my preconceived notion of the probable 

 effects of the drugs. 



THE EFFECT OF THE DRUGS UPON THE GENERAL ACTIVITY OF THE 



RATS 



It is generally stated that large doses of strychnine increase 

 the activity of animals, making them restless and increasing 

 the extent of their reactions to stimuli. I have not found any 



