OH. XLIX.] EQUILIBRATION. 683 



one hemisphere to the other. In the superior peduncle, the degenerated 

 fibres pass chiefly to the tegmcntal nucleus of the opposite side, but partly 

 to that of the same side : in other words, the decussation of these peduncles 

 in the mid-brain is not complete. Some fibres are traceable to the optic 

 thalamus. The middle peduncle is completely degenerated as far as the 

 raphe, where its fibres intermingle with those from the opposite side. The 

 inferior peduncle was stated by Luciani and Marchi to be also degenerated, 

 and these observers traced the fibres down into the cord. But their state- 

 ments have not been confirmed by the most recent and careful work of 

 Ferrier and Risien Russell. If such fibres do exist, their exact course has 

 yet to be discovered (hence the use of a dotted line in fig. 484, p. 651). 

 Some degenerated fibres in the inferior peduncle have been traced to the 

 opposite lower olivary body which completely atrophies, and also to the nucleus 

 of Deiters (see p. 628), the cells of which are probably cell stations on the 

 course of the fibres that emerge from the cerebellum. 



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 



Fig. 506. Pixeen after removal of the cerebellum. (Dalton.) 



weakness ; but the principal symptom observed is inco ordina- 

 tion, chiefly evidenced by a staggering gait similar to that seen 

 in a drunken man. It is called cerelellar ataxy. 



This condition is well illustrated in the above figure (fig. 506) ; 

 the disturbed condition of the animal contrasts very forcibly with 

 the sleepy state produced by removal of the cerebrum (see fig. 494). 



In order that the cerebellum may duly execute its function of 

 equilibration it is necessary that it should send out impulses; this 

 it docs by fibres that leave its cells and pass out through its 

 peduncles ; they pass out to the opposite cerebral hemisphere, and 

 so influence the discharge of the impulses from the cortex of the 

 cerebrum. It is also probable that impulses pass out to the cord 

 (see dotted line in fig. 484), but the exact course of these fibres, 

 if they do exist, has still to be worked out. The only way of 



