722 COMPARATIVE ELECTRO-PHYSIOLOGY 



part to another, a transmission which is now made com- 

 prehensible, being effected through the intervention of the 

 plant-nerves, whose existence I have demonstrated. In 

 the case of trees, again, the interior tissues whose functions 

 are of great importance in various ways, are inaccessible to 

 such external energy as that of light. But no part of 

 them is far removed from the vegetal nerves, whose outer 

 endings are found in the ramified venation of the leaves. 

 The laminae of the plant thus in their aggregation form an 

 extensive catchment-basin for the reception of energy from 

 outside and its ultimate transmission within the plant. An 

 experiment has been described which shows the enhancement 

 of the excitability of the plant-nerve by energy of light 



(fig- 334)- 



I have next to summarise a new method for the study of 

 excitatory reactions in nerves. It has been supposed that in 

 certain respects the reaction of the nerve is specifically 

 different from that of the muscle. It has been regarded as 

 typically non-motile, the highest power of the microscope 

 being incapable, it was said, of detecting any effect in respon- 

 sive change of form. I have shown, however, that this 

 conclusion was erroneous, there being in this respect a con- 

 tinuity between the responses of muscle and nerve. In 

 a particular case of frog's nerve the responsive contraction 

 under strong stimulation was as much as 14 per cent, of the 

 original length, and in others, it was as much as 20 per cent, 

 or more. With a magnification of about 200 times, which is 

 afforded by my moderately sensitive Kunchangraph, the 

 observer is able to study all the excitatory phenomena in 

 nerve with as great ease, and much greater accuracy, as 

 by the employment of a very highly sensitive galvanometer. 

 Records of the electrical responses of nerve are obtained by 

 the differential effects of excitation at the two contacts, when 

 one of these has been subjected to injury. It has been 

 shown that such injury does not always completely abolish 

 the excitability of the second contact, for which reason there 

 may be induced a local reaction of feeble negative or reversed 



