230 Prof. Bose and Mr. Das. Physiological Investigations with 



stimulation of normal specimens is thus seen to depress temporarily the 

 conducting power. 



Action of Injury on Sub-tonic Specimens. — I will now describe a very 

 interesting experiment which shows how an identical agent may, on account 

 of difference in the tonic condition of the tissue, give rise to diametrically 

 opposite effects. In demonstrating this, I took a specimen in a sub-tonic 

 condition, in which the conducting power of the tissue was so far below 

 par, that the test-stimulus applied at a distance of 15 mm. failed to be 

 transmitted (fig. 15). The end of the petiole at a distance of 1 cm. beyond 



Fig. 15. — Effect of injury in enhancing the conducting power of a sub-normal sjDecimen ; 

 (1) Ineffective transmission becoming effective at (2) after section, (3) decline after 

 half an hour, and (4) increased conductivity after a fresh cut. 



the point of application of test-stimulus was now cut off. The after-effect of 

 of this injury was found so to enhance the conducting power that stimulus 

 previously arrested was now effectively transmitted, the velocity being 

 25 mm. per sec. This enhanced conducting power began slowly to decline, 

 and after half an hour the velocity had declined to 4-1 mm. per sec. The 

 end of the petiole was cut once more, and the effect of injury was again 

 found to enhance the conducting power, the velocity of transmission being 

 restored to 25 mm. per sec. 



Summary of Results. 



On isolation of a petiole-pulvinus preparation, the shock of operation is 

 found to paralyse its sensibility. After suitable mounting the excitability is 

 restored, and remains practically uniform for about 24 hours. After this a 

 depression sets in, the rate of fall of excitability becomes rapid 40 hours after 

 the operation, sensibility being finally abolished after the fiftieth hour. 



Experiments carried out on the effect of weight, and the influence of 

 selective amputation of the upper and lower halves of the pulvinus, show 

 that in determining the rapidity of fall of leaf, the assumed factors of the 

 expansive force of the upper half of the pulvinus and the weight of the 

 leaf are negligible compared to the force of active contraction exerted by 



