750 FUNCTIONS OF THE CEREBELLUM [CH. LL 



and eyes to the right : the subsidiary centres or subordinate officials 

 arrange that this is to be accomplished by the external rectus of the 

 right eye supplied by the right sixth nerve, the internal rectus of the 

 left eye supplied by the left third nerve, and numerous muscles of 

 neck and back of both sides supplied by numerous nerves. The 

 relaxation of the antagonistic muscles has also to be provided for. 

 We thus see how the complicated intercrossing of fibres and connec- 

 tions of the centres of the various nerves are brought into play. 



The functions of the cerebellum are investigated by the same two 

 methods of experiment (stimulation and extirpation) which are 

 employed in similar researches on the cerebrum. The anatomical 

 connections of the cerebellum with other parts of the cerebro-spinal 

 axis by its three peduncles have been already considered on p. 684. 



FIG. 458. Pigeon after removal of the cerebellum. (Dalton.) 



In some of the lower animals the vermis is practically the 

 only part of the cerebellum which is present, and it is this part of 

 the cerebellum which is principally concerned in the coordination 

 of the bodily movements. The cerebellar hemispheres are especi- 

 ally connected with the opposite cerebral hemispheres; and just 

 as the different regions of the body have corresponding areas in the 

 cerebrum, so also they are similarly represented in the cerebellum ; 

 but it does not appear necessary from the practical standpoint to go 

 here into the scanty and disputed details of cerebellar localisation 

 already discovered. 



If the cerebellum is removed in an animal, or if it is the seat of 

 disease in man, the result is a condition of slight muscular weak- 

 ness ; but the principal symptoms observed are loss of muscular tonus 

 and a condition of incoordination, chiefly evidenced by a staggering gait 

 similar to that seen in a drunken man. It is called cerebellar ataxy. 



This condition is well illustrated in the figure (fig. 458); the 



