X COMPARATIVE ELECTRO-PHYSIOLOGY 



ment, which I have set forth in the present volume. 

 The reactions of different tissues have hitherto been re- 

 garded as specifically different. As against this, a continuity 

 has here been shown to exist between them. Thus, nerve 

 was universally regarded as typically non-motile ; its re- 

 sponses were believed to be characteristically different from 

 those of muscle. I have been able to show, however, that 

 nerve is not only indisputably motile, but also that the 

 investigation of its response by the mechanical method is 

 capable of greater delicacy, and freedom from error, than 

 that by the electrical. The characteristic variations in the 

 response of nerve, moreover, are, generally speaking, similar 

 to those of the muscle. It has been customary, again, to 

 regard plants as devoid of the power to conduct true excita- 

 tion. But I have shown that this view is incorrect. Experi- 

 ments have been described, showing that the response of 

 the isolated vegetal nerve is indistinguishable from that of 

 animal nerve, throughout a long series of parallel variations 

 of condition. So complete, indeed, has that similarity 

 between the responses of plant and animal, of which this 

 is an instance, been found, that the discovery of a given 

 responsive characteristic in one case has proved a sure guide 

 to its observation in the other, and the explanation of a 

 phenomenon, under the simpler conditions of the plant, has 

 been found fully sufficient for its elucidation under the more 

 complex circumstances of the animal. 



Many anomalous conclusions, with regard to the response 

 of certain animal tissues, had arisen from the failure to take 

 account of the differential excitability of anisotropic organs. 

 Now this is a subject which, in the case of the simple plant 

 organ, is capable of very exact investigation. I have been 



