THE CEREBELLUM 275 



fibers in the posterior columns of the cord through the resti- 

 form bodies of the medulla. 



Function. The only characteristic phenomenon invariably 

 following removal of the cerebellum is an inability to coor- 

 dinate the voluntary muscular movements. The foot, for 

 example, can be raised, and the voluntary muscular act con- 

 cerned in raising it may be as vigorous as ever, but the ani- 

 mal cannot so govern his movements as to know where he put 

 it down. Even the coordination necessary in standing is lost, 

 and the maintenance of the equilibrium is very difficult, if not 

 impossible. The so-called muscular sense is abolished, and, 

 while the power to contract the muscles remains, the animal 

 cannot contract them in a regular or coordinate manner. 

 When it is remembered that wellnigh every voluntary act 

 requires concerted or consecutive muscular movements some 

 idea is gotten of the helpless condition sequent upon such 

 a lesion. If it be granted that there is a center presiding 

 over the coordination of the voluntary muscles, that center 

 is in the cerebellum, and an animal deprived of this organ is 

 as powerless, so far as this function is concerned, as a per- 

 son is to see when the optic centers are destroyed. Its action 

 is crossed. 



It has been noted already that lesions of the posterior 

 white columns of the cord are followed by disturbances of 

 coordination, and that the cerebellum is connected with these 

 columns through the inferior peduncles and restiform bodies. 

 Fibers in these columns serve only as anatomical connec- 

 tions by which the coordinating center communicates with 

 the muscles whose movements it is to regulate, and of ne- 

 cessity any lesion of these fibers destroying that connection 

 is followed by the loss of control of the center over the mus- 

 cles. However, in degeneration of the posterior columns 

 (locomotor ataxia) an effort at coordination can be made, 

 so that progression is possible by the aid of fixed attention. 

 It is possible also that the coordinating messages are carried 

 in such cases by the motor fibers, though in an unsatisfactory 

 manner. 



