944 



THE CENTRAL NERVOUS SYSTEM 



logical development of the corresponding groups of muscles. All 

 this fits in well with the idea that the cerebellum is a great reflex 

 mechanism standing in intimate relation on the one hand to numer- 

 ous afferent paths (skin, muscles, labyrinth, etc.), and on the other 



to the voluntary muscles. It is 

 the precise nature of the influence 

 exerted by it upon the latter 

 which is in doubt, whether an 

 augmenting sthenic influence, as 

 Luciani supposes, or a co-ordinat- 

 ing influence, as Flourens assumed, 

 or a combination of these. 



Progress has recently been made 

 in utilizing the results of experi- 

 mental and clinical study of the 

 cerebellum for the localization of 

 circumscribed cerebellar lesions in 

 Fig. 380. Localizations on the Inferfe- man (Baranv) 



lateral Aspect of the Human Cere- _^ t * v v 



bellum (Barany). x , is a centre for -Lhe centres for the limbs are 

 the tonus of the muscles abducting situated in the cortex of the hemi- 



the right arm; O a centre for the spher e S) those for the right 6X- 

 tonus of the muscles concerned m ... , . , ., 



adduction of the right hand ; + , a trermties in the right semilunar 

 centre for the tonus of the muscles (superior and inferior) and digas- 



adducting the right arm; a centre tric l obu l es ; those for the left 

 for the tonus of the muscles adducting ... .. 



the right hip. N.v, N.VI, N.vn, extremities in the corresponding 

 N.IX, N.XII, are cranial nerves. positions on the left cerebellar 



hemisphere. 



Forced Movements. We have incidentally mentioned that in fishes 

 injuries to the semicircular canals may give rise to movements which 

 seem to be beyond the control of the animal, and which have conse- 

 quently received the name of 

 ' forced movements.' It may 

 be added that when the in- 

 ternal ear of a Necturus (one 

 of the tailed amphibia) is 

 destroyed on one side, rapid 

 movements of rotation around 

 a longitudinal axis are ob- 

 served. The animal spins 

 round and round apparently 

 without voluntary control, 

 purpose, or fatigue. The di- 

 rection of rotation is towards 

 the side of the lesion, the 

 observer being supposed to 

 look down upon the animal as 

 it lies in its normal position. 

 After a time it becomes quiescent; but the forced movements can be 

 again produced by pinching or exciting it in other ways. Similar 

 rolling movements, and in the same direction, have been observed in 



Fig. 381 Localizations on Posterior Aspect 

 of Human Cerebellum (Barany). &, a centre 

 for the tonus of the muscles concerned in 

 the movements of the right arm downwards; 

 X , same as in Fig. 380. 



