732 COMPARATIVE ELECTRO-PHYSIOLOGY 



cessation of stimulus this will give luminous response, which 

 may be taken as the immediate effect of primary stimulus. 

 On the fading of this image, if the whole plate be subjected 

 to feeble diffuse illumination for a short time, the latent image 

 will once more appear as a bright patch against a dark back- 

 ground. This is because, as the after-effect of stimulus, the 

 area B has been rendered more excitable. Hence, diffuse 

 stimulation evokes more intense response from it than from 

 its more inert background. Similarly, the memory-image 

 is capable of revival by the internal impulse of the will, 

 acting as a diffuse stimulus to evoke a differential sen- 

 sation, which reproduces the light and shade of the primary 

 picture. 



The responsive phenomena seen in living matter are, 

 undoubtedly, wonderful and mysterious ; but those shown 

 by the inorganic are no less wonderful. By ascribing all 

 physiological occurrences to specific reactions, and by con- 

 stantly postulating the intrusion of forces of a new order, 

 the road to the further advancement of knowledge is closed. 

 By the conception of matter itself, on the other hand, as 

 possessed of sensibility that is to say, of molecular respon- 

 siveness we attain an immediate accession of insight into 

 those physical interactions which must furnish the terms of 

 any ultimate analysis. We are led by it to the discovery 

 of the impressive fact of continuity as existent between the 

 responses of the most complex living, and the simplest 

 inorganic matter. Limiting ourselves, again, to the realm of 

 living matter, we are impelled to recognise parallelisms, in 

 the response of plant and animal, whose extent could never 

 otherwise have been suspected. All the responsive phe- 

 nomena of the animal are thus found to be foreshadowed in 

 the plant, and this to such a degree that in the common 

 script of the response-record the one is indistinguishable 

 from the other. In both we observe a similar series of 

 excitatory effects, whether these be exhibited mechanically 

 or electrically. Both alike are responsive, and similarly 

 responsive, to all the diverse forms of stimulus that impinge 



