VELOCITY OF TRANSMITTED IMPULSE 149 



the variation of conductivity, under variation of tempera- 

 ture. The plant was maintained at the required tempera- 

 tures in the thermal chamber, either by the cooling device 

 or by the electrical appliances for heating, which have been 

 previously described. In fig. 88 time-records are given of 

 the transmission of excitation at the three temperatures of 

 22° C, 28° C, and 31° C. This experiment was carried out 

 in the Calcutta winter, when the temperature of the room 

 was 22° C. The normal velocity of transmission in the plant 

 was thus, owing to the season, somewhat low. Stimulus 

 of maximal intensity 2 was applied, at a distance of 

 10 mm. from the responding point. The lowest of the 



Fig. 88. — Effect of temperature in enhancing velocity of transmission. 

 Three records, from below upwards, are for temperatures 22° C, 

 28° C, and 31° C. respectively. 



three records gives us the period of transmission at 

 the temperature of 22° C. The next record was taken 

 at 28° C, and the third or topmost at 31° C. It is quite 

 evident from these figures that the velocity is continuously 

 increased under rising temperature. The period taken at 

 22° C. was 2*94 seconds ; at 28° C, 1-69 second ; and at 

 31° C, 1*2 second. We noted in a former experiment 

 that the latent period undergoes a variation with changes 

 of temperature. Thus in a given experiment, while the 

 latent period at 23° C. was -165 second, at 28° C. it was 

 •12 second, and at 33° C, -065 second. These variations are 

 very slight as compared with the total time required for the 



