692 PHYSIOLOGY. 



He suffers intense vertigo, with loss of balance, which renders all cf his 

 movements ataxic. This is especially so of motions of locomotion. 



From this it would seem that the cerebellum is the center of the 

 coordination of movements. With the cerebellum destroyed, the ani- 

 mal can no longer balance itself. Atrophy of one cerebellar hemi- 

 sphere follows atrophy of the opposite cerebral hemisphere,, showing 

 a close relation between them. 



The function of equilibration is regulated by the cerebellum, 

 which receives afferent impulses as follows : 



1. Tactile impressions by the posterior columns to the nuclei of 

 Goll and Burdach and from them by the restiform body to the cere- 

 bellum. To prove that tactile impressions are necessary to coordina- 

 tion it is simply necessary to remove the skin from a frog, when it 

 will not be able to leap, swim, or resume its natural position when 

 placed on its back. In locomotor ataxia, where we have a sclerosis 

 of the posterior columns, there is great difficulty in walking. 



2. Visual impressions by optic nerve conveyed by the superior 

 cerebellar peduncle. Ataxies are able to walk much better when they 

 fix their eyes on the ground, and when they close their eyes walking 

 becomes impossible. 



3. Muscular-sense impulse through the direct cerebellar tract by 

 the restiform body to the vermis. 



4. Impressions from the semicircular canals, which will be con- 

 sidered under the "Semicircular Canals." Here the vestibular nerve 

 carries impressions from the semicircular canals by the restiform body 

 to the nucleus fastigii and nucleus globosus of the cerebellum. 



Horsley has shown that the cortex cerebelli is the afferent 

 recipient organ, and that the cerebellar nuclei and the paracerebellar 

 or bulbar nuclei are the efferent mechanisms of the cerebellum. The 

 cortex cerebelli sends no direct axons via the cerebellar peduncles 

 to the brain or spinal cord. The cortical efferent axons terminate 

 in the intrinsic nuclei of the cerebellum, that is, the nucleus den-' 

 tatus, nucleus fastigii, and nucleus emboliformis vel globosus. These 

 intrinsic nuclei send efferent axons to the cerebral, spinal, and 

 paracerebellar, that is, bulbar nuclei. 



EFFERENT TRACTS OF THE CEREBELLUM. An efferent tract from 

 the cerebellum may be as follows: the fibers of the superior pedun- 

 cles end in the red nucleus ; the rubro-spinal tract runs from the red 

 nucleus, decussates, passes through the medulla and pons, enters the 

 lateral column, and terminates around the cells of the anterior horns. 

 It is also known as Monakow's bundle. Another efferent tract may 



