164 COMPARATIVE PHYSIOLOGY OF THE BRAIN 



animal can go backwards easily, while forward move- 

 ment is difficult. In fact it is apparent that if the 

 animals attempt to move in any direction while 

 the current is passing through them they go toward 

 the anode. 1 



From this fact it follows that, for the nervous appa- 

 ratus of the progressive movements of Amblystoma, a 

 close relation must exist between the orientation of 

 the determinative elements of the motor nerves and 

 their function : in fact the nervous elements which 

 cause the progressive movements must have with re- 

 gard to the longitudinal direction of the animal an 

 orientation which is opposite to the orientation of 

 those elements which cause the backward movement. 

 Garrey and I had called attention to the fact that the 

 observations of Blasius and Schweitzer show that 

 other Vertebrates, for instance, young eels, behave 

 like Amblystoma. The same also holds good for the 

 shrimp. This last assertion is based upon a series of 

 experiments made by Maxwell and myself (2). These 

 experiments were made chiefly on Palaemonetes. This 

 Crustacean uses the third, fourth, and fifth pairs of legs 

 for its locomotion. The third pair pulls in the for- 

 ward movement and the fifth pair pushes. The fourth 

 pair generally acts like the fifth and requires no further 

 attention. If a current be sent through the animal 

 longitudinally, from head to tail, and the strength in- 

 creased gradually, a change soon takes place in the 



1 This explains the galvanotropic gatherings observed by Hermann, Blasius 

 and Schweitzer, and others. 



