250 COMPARATIVE PHYSIOLOGY OF THE BRAIN 



and the roots of many plants. It lives chiefly in 

 cracks. This is no more a process of consciousness 

 than the boring of a root in the sand. It exists in 

 every segment of the eel, and if touched on one side 

 with the finger positively stereotropic curvations 

 toward the finger ensue. The stimulus of rubbing 

 increases the tension of the muscles on the stimulated 

 side. But while it is positively stereotropic it is not 

 positively thermotropic. If a burning object is applied 

 it produces a relaxation of those muscles which move 

 the body toward the stimulated side. 1 The body is 

 thus moved toward the opposite side. In this case 

 too consciousness plays no more part than it does in 

 the tropic reactions of a plant. The whole discussion 

 of the " spinal-cord-soul " was needless, and might have 

 been avoided if Pfluger had realised that those phe- 

 nomena which the metaphysician calls consciousness 

 are a function of the mechanism of associative mem- 

 ory. In that case the question would have been : 

 Does the decapitated animal still possess associative 

 memory, or are its reactions all due to inherited struct- 

 ures and irritabilities ? With the aid of comparative 

 physiology it would have been found that all the reac- 

 tions of such an animal may occur in forms which 

 possess no associative memory. The mechanisms 

 which allow an associative memory in Vertebrates 

 seem to be located in the cerebral hemispheres. In 



! If Pfluger had made his experiments on decapitated snakes he would have 

 obtained different results. Exner mentions that such animals press their body 

 against a fiery coal just as well as against the finger (13). 



