EFFECTS OF STRYCHNINE UPON RATE OF LEARNING 149 



concentration of strychnine which notably increases the general 

 activity of the rat. After the minimum lethal dose the ani- 

 mals crouch on the floor of the cage and remain unusually quiet, 

 unless stimulated, until the onset of convulsions. At the same 

 time the irritability to auditory stimuli is very much increased, 

 and the slightest noise will make them leap high in the air. 



The dose of 0.10 mgm., like the lethal dose, seems to reduce 

 spontaneous activity and to lower the threshold to auditory 

 stimuli. 3 After five to ten minutes a coarse tremor, which may 

 be so marked as to resemble a scratching reflex, is visible when 

 the rat raises one foot from the floor. At the same time a 

 marked incoordination of movement appears. The animals 

 are unable to leap accurately or to prevent themselves from falling 

 from the experimenter's hands, and in walking their feet are 

 set down heavily so that the sound may be heard at some dis- 

 tance. When they are frightened their movements become 

 badly incoordinated and even convulsive. 



The computation of the rate of running in the maze shows that 

 they move slowly. Besides this they frequently show a char- 

 acteristic slowing of movement and hesitation when approach- 

 ing the turns in the maze, so that their progress is a series of 

 quick dashes, alternating with pauses ten seconds or more in 

 length at the turnings of the maze. This behavior may be 

 present even when errors are no longer made. 



This description applies to the majority of the animals in 

 group A, experiment 1 (table 1). The animals in the second 

 experiment (group E) rarely showed any such activities, and 

 my notes on them reiterate from day to day "no perceptible 

 effect of the drug." Tremor was sometimes noted but only 

 two of the sixteen showed hesitation at the turns of the maze. 

 The animals used in the second experiment were bred during 

 the winter and were older and much larger than those used in 

 the first experiment. Since in the two experiments the dose 

 was not regulated to the weight of the animals it is almost 

 certain that it was relatively smaller for the group E than for 



3 Probably the excitability to other stimuli is also increased, but this is more 

 difficult to determine. 



