CHARACTER OF TRANSMITTED IMPULSE 167 



plate. In the next record (fig. 93) a series of response-records 

 to transmitted excitation were taken on a slower-moving 

 plate. The testing stimulus was always the same, the 

 difference being that the electrotonic block was ' off ' and 



Fig. 93. — Records of transmitted excitation with the block 

 off and on. Arrest of transmitted excitation under 

 electrotonic block at b, b. 



' on ' alternately. It will be noted that the excitation was 

 invariably arrested whenever the block was appUed at b, b. 



Block of Conduction by the Action of Poison 



(i) Experiment with Biophytum sensitivum 



Reference has been made to the inconclusive character 

 of Pfeffer's narcotisation experiment. The ineffectiveness 

 of the block, it was explained, might have been due to the 

 thickness of the tissue preventing free access of the anaesthetic 

 to the conducting-elements in the interior. It occurred to 

 me that the physiological block induced by a drug could be 

 rendered more effective in two different ways : first, by the 

 selection of a thin petiole in which access of the solution 

 to the interior by absorption would be less difficult ; and, 

 second, by the employment of strong toxic agents like 



