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 



