li>0 Professor Jagadis Chunder Bose [May 



^!). 



and that the latent period is O'l second. Hence the true time for 

 the excitation to travel through a distance of 30 mm. is I'T) second, 

 the velocity being 20 mm. per second. 



The velocity of excitatory impulse in the plant is slower than those 

 of higher, but quicker than those of lower animals. The speed of 

 the impulse is, however, suV^ject to variation under different condi- 

 tions. One significant result that came out was that while a plant 

 carefully protected under glass from outside blows looked sleek and 

 flourishing, yet as a complete and perfect organism it proved to be a 

 failure. Its conducting power was found atrophied or paralysed. 



Fig. 13. — DetebmijStation of Velocity of Transmission 

 IN Mimosa. The two lower records are in response to 

 stimulus applied at a distance of 30 mm. ; the upper 

 record exhibits latent period in response to direct 

 stimulus applied on the pulvinus. Successive dots in 

 this and following records are of intervals of one-tenth 

 part of a second. 



But when a succession of blows rained on this effete and bloated 

 specimen, the stimulus canalized its own path of conduction and it 

 became more alert and responsive, and its nervous impulses became 

 very much quickened. 



Influence of Tempeeature on Velocity. 



A decisive experiment to discriminate between the theories of 

 mechanical and nervous transmissions consists in the determination 

 of the effect of temperature on the speed of transmission. Tempera- 

 ture has no effect on mechanical propagation, whereas a moderate 

 variation of it profoundly affects nervous transmission. The result 

 given in Fig. 14 is quite conclusive as regards the excitatory 

 character of the impulse in plants. It is seen that with rising 



