FUNCTIONS OF THE BRAIN 935 



but in the deeper parts of the body (labyrinth of ear, muscles, 

 tendons, joints, viscera, etc.) (p. 914). After removal of the whole 

 cerebellum (in the dog or monkey), there is at first rigidity and tonic 

 spasm of certain muscles, which contribute to the difficulty of co- 

 ordinating their movements. When this stage has passed, the 

 muscles all over the body, but especially those of the loins and hind- 

 limbs, and those which fix the head, are weaker than normal (as- 

 thenia), are deficient in tone (atonia), and contract with a peculiar 

 want of steadiness (Luciani). When one lateral half of the cere- 

 bellum is removed, the symptoms affect especially the muscles on 

 the same side. In extensive lesions of the cerebellum in man what 

 has been noticed is a marked inability to maintain the upright 

 posture, giddiness, a staggering gait, twitching movements of the 

 eyes (nystagmus), tremor accompanying voluntary movements 

 in a word, a general breakdown of the co-ordinating machinery 

 (asynergy or asynergia), and especially of the part of it concerned 

 in the movements necessary for locomotion, and for the maintenance 

 of the equilibrium of the body the so-called cerebeMar ataxia. 

 There is no sensory paralysis and none of voluntary movement 

 such as lesions of the cerebral cortex produce, nor is there any 

 psychical disturbance. In cases of congenital defect of the cere- 

 bellum, the power of walking, and even of standing, may be late in 

 being acquired, and imperfect. But it is remarkable what great 

 deficiencies in the cerebellar substance are often compensated for 

 when established early in life, so that even cases of marked atrophy 

 or lack of development have sometimes been recognized for the 

 first time at the necropsy. 



The connections of the cerebellum with other parts of the central 

 nervous system and with the periphery corroborate the direct 

 results of experiment. For, in addition to the visual impressions, 

 the most important afferent impulses concerned in equilibration are 

 those from the semicircular canals and vestibule of the internal ear, 

 the muscles, tendons, joints, etc., and certain portions of the skin, 

 such as that of the soles of the feet. And the cerebellum, as we have 

 seen (p. 885), is linked with all of these, and has besides an extensive 

 crossed connection through the middle and superior peduncles with 

 the opposite cerebral hemisphere. The importance and extent of 

 this crossed connection with the great brain is illustrated by the facts 

 that in disease atrophy or deficient development of one cerebellar 

 hemisphere is associated with a similar c6ndition of the opposite 

 cerebral hemisphere, and that a lesion in one-half of the cerebellum 

 affects chiefly the co-ordination of the movements of the same side 

 of the body that is to say, of the side connected with the opposite 

 cerebral hemisphere. 



We do not as yet know the full significance of this extraordinarily 

 free communication of the grey matter of the cerebellum with every 

 part of the central nervous system. But it is evident that by the broad 



