622 Dynamic Theory. 



looking steadily at a swiftly moving body of water, prove the influence 

 of optic stimulations in the balancing functions. The dependence is 

 not mutual, however, for lesions of the cerebellum have no effect upon 

 the eyesight, never produce blindness. 



The sense of feeling, or tactile sense, including heat, pressure and the 

 muscular sense, is, of course, a necessary factor in the function of 

 equilibration and co-ordination. Tactile impressions reach the cere- 

 bellum by way of the olivary bodies and restiform tracts of the me- 

 dulla oblongata. Injury to the restiform tracts disturb equilibrium in 

 the same way in which* it is done by injury to the semicircular canals, 

 with rolling and tumbling motion of the body, and turning of the eyes; 

 nevertheless the cerebellum has nothing to do with conscious sensation 

 of touch, and injury to it does not impair tactile sensation. Neither 

 does section of the restiform tracts, nor of the connected posterior col- 

 umns ; the restiform bodies being related with the posterior columns 

 through the olivary bodies, the restiform of one side being connected 

 mainly with the posterior column of the opposite side. 



The fibres of the p} T ramidal tracts of the medulla oblongata which 

 cross each other in the pons varolii, are those which relate to the cere- 

 bral hemispheres only. Those which form connections with the cere- 

 bellum are not crossed, so that a stimulation which involves both cere- 

 brum and cerebellum will affect the right lobe of the cerebellum, and 

 the left hemisphere of the cerebrum, or vice versa. See fig. 375, which 

 shows an example of the decay of the cerebellum, following and conse- 

 quent upon loss of function in the cerebrum, and also shows the normal 

 subordination or correspondence of the functions ( or some of them ) of 

 the former to the latter. Ferrier remarks that the ' ' functions of the 

 cerebellum are outside of the sphere of mind proper, as expressed in 

 sensation, emotion, volition and intellect. " 



If the peduncles of the cerebellum be divided, the effect is a rolling 

 motion of the animal sidewise and very rapid. If the peduncle be di- 

 vided from behind, that is, the portion derived from the restiform col- 

 umn called the posterior peduncle, the rolling is towards the side on 

 which the injury is made. ( See figs. 267, 271, 273.) But if the sec- 

 tion be made in front, in the anterior peduncle, the turning is from that 

 side towards the other. This difference is supposed to be caused by the 

 fact that the fibres of the anterior peduncle connect largely with the de- 

 cussating fibres of the anterior pyramids of the medulla oblongata, so 

 that the anterior peduncle of one side, and the posterior peduncle of 

 the other, connect with the same tract of motor .nerves. The sever- 

 ance of the posterior peduncle, or part of it, disconnects the cerebellum 

 from the afferent stimuli, through the restiform columns, while the sev- 

 erance of the anterior peduncles cuts off an outgoing stimulus to certain 



