408 



HARRY THOMAS FOLGER. 



preceded the exposure to illumination, while it responded 5 times 

 out of 5 trials when previous stimulation by mechanical shock was 

 lacking. These results are entirely in accord with previous ob- 

 servations and leave no doubt that mechanical shock does affect 

 the response to light. 



Table II. is the record of an experiment in which the procedure 



TABLE II. 



SHOWING THE EFFECT OF SUDDEN ILLUMINATION UPON THE RESPONSE TO 



MECHANICAL SHOCK. 



In each trial the animal was subjected to a mechanical shock, and in every 

 other one it was illuminated before being exposed to shock. Three minutes 

 were allowed between tests. 



Individ- 

 ual No. 



1 Mechanical shock alone 5 



Mechanical shock following immediately after 



sudden illumination 6 



2 Mechanical shock alone 6 



Mechanical shock following immediately after 



sudden illumination 8 



3 Mechanical shock alone 6 



Mechanical shock following immediately after 



sudden illumination 6 



4 Mechanical shock alone . 4 



Mechanical shock following immediately after 



sudden illumination 6 



Totals Mechanical shock alone 21 



Mechanical shock following immediately after 



sudden illumination 26 



Number 

 of Trials. 



No Re- 

 actions. 



o 



4 



i 



4 



2 



16 



in the experiment just described was reversed. Here tests in 

 which the animal was stimulated by illumination and immediately 

 on the resumption of movement given a mechanical shock alter- 

 nated with tests in which a mechanical shock alone was used as 

 the stimulating agent. As shown in the table, individual No. I 

 reacted 5 times out of 5 trials when stimulated by mechanical 

 shock alone, while it reacted to the same stimulus only 3 times 

 out of 6 trials when the mechanical shock was preceded by ex- 



