EXPERIMENTS ON AR THROPODS 1 1 7 



They, however, make no progressive movements. I 

 believe this is due possibly to a secondary effect of 

 the extirpation of the supracesophageal ganglion. 

 The legs of such an animal have an abnormal posi- 

 tion, being more strongly flexed at the joints nearest 

 the body than they are normally. The tension of 

 the extensors probably suffered severely from the 

 operation. Such mechanical disturbances might easily 

 cause difficulty in locomotion, while simple pendulum- 

 movements of the legs, which require practically no 

 labor, could still be performed. The fact that after re- 

 moval of the brain of crayfish the tension of the flex- 

 ors predominates in certain joints is of interest, as we 

 meet with the same phenomenon in dogs that have 

 lost the anterior region of the cerebral hemispheres, 

 and as it also comes to our attention in man after 

 apoplexies which result in the paralysis of an arm. 



Bethe concludes from these pendulum-movements 

 that the brain is an organ of inhibition. As regards 

 this, the remarks hold good that have already been 

 made in this connection on annelids (see p. 94). 



The weakening of the muscles in the crayfish whose 

 brain has been extirpated shows itself also in the fact 

 that the forceps no longer pinch as hard as those of 

 normal animals. 



After what has been said concerning the segmental 

 character of the central nervous system, it is to be 

 expected in the crayfish that, since the segmental 

 ganglia of the organs of mastication are located in 

 the subcesophageal ganglion, extirpation of the supra- 



