RESPONSE BY SENSATION 733 



upon them. We ascend, in the one case as in the other, 

 from the simplicities of the isotropic to the complexities of 

 the anisotropic ; and the laws of these isotropic and aniso- 

 tropic responses are the same in both. The responsive 

 peculiarities of epidermis, epithelium, and gland ; the re- 

 sponse of the digestive organ, with its phasic alternations ; 

 and the excitatory electrical discharge of an anisotropic 

 plate, are the same in the plant as in the animal. The 

 plant, like the animal, is a single organic whole, all its 

 different parts being connected, and their activities co-ordi- 

 nated, by the agency of those conducting strands which are 

 known as nerves. As in the plant-nerve, moreover, so also 

 in the animal, stimulation gives rise to two distinct impulses, 

 exhibiting themselves by twofold mechanical and electrical 

 indications of opposite signs. It is the nature of the indica- 

 tor, again, which determines in any given instance the form 

 of the responsive expression. A single molecular derange- 

 ment may thus find manifestation as change of form, alteration 

 of electrical condition, and subjective sensory variation. The 

 dual qualities or tones known to us in sensation, further, are 

 correspondent with those two different nervous impulses, of 

 opposite signs, which are occasioned by stimulation. These 

 two sensory responses positive and negative, pleasure and 

 pain are found to be subject to the same modifications, 

 under parallel conditions, as the positive and negative 

 mechanical and electrical indications with which they are 

 associated. And finally, perhaps, the most significant 

 example of the effect of induced anisotropy lies in that 

 differential impression made by stimulus on the sensory 

 surfaces, which remains latent, and capable of revival, as the 

 memory-image. 



In this demonstration of continuity, then, it has been found 

 that the dividing frontiers between Physics, Physiology, and 

 Psychology have disappeared. 



