312 KANSAS UNIVERSITY SCIENCE BULLETIN. 



on the injured side is folded ; that on the uninjured is partly 

 spread. The animal may have been sluggish before the opera- 

 tion, but immediately afterward it is very active, moving in a 

 circle toward the uninjured side. If it is placed on a table, 

 with its left side very close to the edge, and stimulated, espe- 

 cially by touching the palps on the operated side, which are 

 now more sensitive and produce more marked reflex responses 

 than those on the unoperated side, it will at once fall from the 

 table. The direction in which the animal hops may be either 

 toward the left or the right, but shortly after the operation it 

 hops usually toward the unoperated side. When placed on its 

 back it turns over, but not so readily as does the normal animal. 

 About five hours after the loss of half of the brain, it is no- 

 ticed that the hopper stands more erect ; that is, inclines less 

 strongly toward the unoperated side, and, by close inspection, 

 it is seen that the legs on the operated side are not flexed so 

 much as they were. Pressing either palps, wings, legs or the 

 irritable antenna now causes the animal to move in a nearly 

 straight line. Yersin and Bethe observed that insects that had 

 half of the brain destroyed would gradually lose the inclined 

 posture and respond finally to a strong stimulus by going either 

 to the right, left or straight forward, depending upon the region 

 stimulated. Bethe believes that the appendages on the oper- 

 ated side are weaker, and their reflexes are less inhibited than 

 those on the unoperated side. His explanation is that the 

 brain exercises a tonus over the muscles and an inhibition over 

 reflex movements. When half of the brain is removed, there- 

 fore, the muscles on the operated side lose their tonus, become 

 weaker, and the reflex responses are no longer inhibited, as 

 they are in the normal animal. This view would explain some 

 of the results of lesion to half the brain, but it does not entirely 

 explain why the flexed position on the injured side gradually 

 disappears. It seems that the flexors of the injured side and 

 the extensors of the uninjured side, are stimulated ; or that the 

 extensors of the operated side and flexors of the unoperated side 

 are inhibited, or have lost their tonus. Moreover, it seems that 

 the same region of the brain controls these muscles which nor- 

 mally act together for a definite movement, and are associated 

 and situated on opposite sides of the body, as, for instance, the 

 flexors of one side and extensors of the other. As a conse- 



