146 DYNAMICS OF LIVING MATTER 



The animals according to these authors choose the position which oc- 

 casions the least pain; namely, with their heads toward the anode. 

 This assumption is contradicted by the above-mentioned experiences 

 on the effects of the galvanic current on the brain of human beings, 

 which show that the tendency to fall toward one side is not produced, 

 and not even accompanied, by any sensation of pain. Moreover, the 

 above-mentioned observation on the effects of the current on the ten- 

 tacles of Polyorchis, the reactions of Paramacium, and the observations 

 on Pal&monetes, show that these reactions find their adequate explana- 

 tion in the direct effects of the current upon the organs or nervous 

 mechanism of locomotion ; that there is no room left for the smuggling 

 in of hypothetical pain sensations between the current and its effect 

 upon the mechanism of locomotion. I have repeatedly pointed out 

 that it is superfluous, and often in direct contradiction to the facts, 

 to assume the existence of human sensations in lower animals, and to 

 put these hypothetical sensations as a necessary link between the ex- 

 ternal stimulus and its motor effect. It is easy to see what led Blasius 

 and Schweizer to their assumption. If we send a current through a 

 trough in which are found specimens of a Salamander, Amblystoma, 

 the attitude of the animal changes considerably, according to the direc- 

 tion in which the current goes. When the current goes from tail to 

 head, the animal assumes an opisthotonic position, with its mouth 

 open. It is evidently this condition, together with a certain restless- 

 ness, which caused Blasius and Schweizer to assume that the ascend- 

 ing current excites the animal painfully. If we, however, look at the 

 condition of the animal when the current goes from head to tail, we see 

 that in this case the animal is also in a forced position ; namely, with 

 its head downward and its back convex. The right expression of 

 the facts is, it seems to me, that the descending as well as the ascending 

 current change the tension of certain muscles; but while the latter 

 causes the contraction of the extensors of the vertebral column and of 

 correlated muscles, the former causes the contraction of the flexors. 

 The assumption of the pain sensation as the necessary link in the one 

 case and not in the other is quite arbitrary and unnecessary. It is 

 probable that in animals possessing a central nervous system, the 

 galvanotropic reactions are brought about chiefly by the action of the 

 current upon the central nervous system. Since the galvanic current 

 influences not only the superficial layers of an organism like the light, 

 but penetrates through the whole body, the cases of ideal galvanotropic 

 orientation are not so common as those of heliotropic orientation. 



