NERVOUS INTEGRATIONS IN MAN 



257 



Inhibitory influence and that by virtue of its rich receipts 

 from the sensory endings in muscle it exerts an influence 

 appropriate to the particular reaction in progress, so securing 



CEREBELLUM 



OPTIC CHIASN/l 



PITUITARY 3T^LK 



HYPOTH/\L^MUS 



PONS 



MEDULLA 



Fig. 3. Median sagittal section of human brain, showing position beneath 

 cerebral hemispheres of cerebellum, medulla and hypothalamus. 



an orderly adjustment of the movement. When movements 

 are initiated through activity of the cerebral hemispheres, 

 the cerebellum, through its cerebro-ponto-cerebellar con- 

 nections, is notified of the intended act, and adjustments 

 are automatically made to bring about its harmonious 

 execution. The adjustments facihtated by the cerebellum 

 involve regulation of the reciprocal activity of antagonistic 

 muscle groups as well as of the so-called synergic muscles. 



The activity of the cerebellum is not confined to the 

 skeletal muscles; it exerts also a regulatory influence over 

 the eye muscles, the vocal cords, and the muscles of deglu- 

 tition. Destruction of the cerebellum causes, for example, 

 characteristic changes in the voice, the speech becoming 

 thick, monotonous and slurring (ataxia of the laryngeal 

 muscles), and swallowing usually becomes to some extent 

 impaired though not impossible.* It may be, however, that 

 the dysphagia of cerebellar lesions is due, not to destruction 

 of the cerebellum, but to injury of the subjacent centers of 

 the medulla (bulb). 



