THE NEUROMl SCULAR MKCHAN1SM 1)7 



size of the cerebellum can scarcely be correlated with the 

 intelligence of these types; further consideration inclines 

 one to the belief that it is in some sense linked with 

 elaborate and active neuromuscular mechanisms. 



A fish gives little indication of intelligence, but it has a 

 most multifarious muscular system corresponding with 

 its intricately developed skeleton. The bird has much 

 more intelligence, but is distinguished most clearly by its 

 powers of flight. A prominent cerebellum seems always to 

 imply capacity for locomotion and balancing. This gen- 

 eral contention is borne out by the results of experiments 

 in which this part of the brain has been partially or wholly 

 removed. When a physiologist wishes to determine the 

 service of a particular structure in the nervous system 

 he cuts it away, if this is possible, and keeps the animal 

 alive to observe the resulting deficiency. This procedure 

 is justified only when two conditions are fufilled: first, 

 no pathways between other stations than that under ob- 

 servation must be interrupted; second, the effects recorded 

 must be those due to the actual lack of the part which has 

 been sacrificed, and not to the irritation set up at the seat 

 of the operation. 



The pioneer experiments upon the cerebellum were 

 made in France about one hundred years ago. The 

 investigator found that a pigeon recently deprived of this 

 part of the brain gave a distressing picture of incoordina- 

 tion. The bird could not fly nor even keep its feet. Its 

 struggles were painful to witness, and the more so because 

 there seemed to be no lessening of the normal sensitive- 

 ness and capacity for terror. In its staggering and flut- 

 tering about there was no apparent loss of the power to 

 contract individual muscles, but the most obvious loss 

 of the ability to secure the needful cooperation of the 

 groups on whose action equilibrium in rest or motion 

 depends. The doctrine based on such observations was 

 to the effect that the cerebellum is in charge of the general 

 musculature so far as this, is used for equilibration and 

 perhaps for other habitual types of performance. 



7 



