724 FUNCTIONS OF THE CEREBELLUM. 



Some of this substance is more condensed to form a UmUans externa on the surface of the 

 cerebellum, while on the boundary line next the granular layer the branches of the glia-cells 

 form a limitam interna, and between the two stretches the neuro-keratin network. Some 

 small varicose nerve-fibres exist in this layer continuous with those in the granular layer. The 

 branched process of the cells of Purkinje is tibrillated, and the finer processes are composed 

 also of fibrils, which are gradually distributed until they become isolated. It is suggested by 

 Beevor that these fibrils bend at a right angle in a plane parallel to the surface, and rearrange 

 themselves as fibres surrounded by a medullated sheath, and that these fibres run inwards 

 through the molecular and granular layers as the branched fibres to the medulla.] 



Function. Injuries of the cerebellum cause disturbances in the harmony of the 

 movements of the body. Most probably, the cerebellum is a great and important 

 central organ for the finer co-ordination and integration of movements. The fact 

 that it is connected with all the columns of the spinal cord and with all the central 

 ganglionic masses, renders this very probable. The direct cerebellar tracts from the 

 lateral column of the cord conduct sensory impressions to the cerebellum, and thus 

 indicate the posture of the trunk. The cerebellum may affect the motor nerves of 

 the cord through fibres which pass downward in the lateral columns of the cord 

 from the restiform bodies {Flechsig). Injury of the cerebellum neither produces 

 disturbance of the psychical activities, nor does it interfere with the will or 

 consciousness. Injuries to the cerebellum itself do not give rise to pain. 



According to Schifi", the cerebellum does not actually regulate the co-ordination of movements. 

 According to him, there is a mechanism on both sides of the middle line, which increases all 

 the complicated muscular movements not only those for powerful contractions, but also the 

 peculiar fine movements which fix the limbs and joints. Luciaui asserts that destruction of 

 the cerebellum produces a condition of incomplete tonus, there being a want of energy to control 

 the voluntary muscles. Each half of the organ acts on both halves of the body. 



Injury or Removal of Cerebellum. The immediate results produced by injury to 

 or removal of the cerebellum have been admirably described by Flourens (fig. 508). 



On removing the most superficial layers 

 in a pigeon, the animal merely showed 

 signs of weakness and interference with 

 the uniformity of its movements. On 

 removing more of the cerebellum, the 

 animal became greatly excited, and made 

 violent irregular movements, which did 

 not partake of the character of con- 

 vulsions. The sensorium was unaffected, 

 while vision and hearing were intact. 

 Co-ordinated movements, such as walk- 

 : ing, flying, springing, and turning, could 

 riEziz be executed but imperfectly. After re- 

 , F . Tog moval of the deepest layers, the power of 



p; , -*k * lg * u li a executing the above-named movements 



1'igeon with its cerebellum removed. ,,. i i* i i r\ i 



was completely abolished. On placing 



the pigeon on its back, it could not get on its legs ; at the same time it made con- 

 tinually the greatest exertions in its movements, but these were always inco-ordinated, 

 and therefore without any satisfactory result. The will, intelligence, and percep- 

 tion remained intact ; the animal could see and hear, and sought to avoid obstacles 

 placed in its way. It gradually exhausted itself in fruitless efforts to get on its 

 legs, and ultimately remained in its abnormal position, quite exhausted. Flourens 

 concluded from these experiments that the cerebellum is the centre for co-ordinating 

 voluntary movements. Lussana and Morganti regard the cerebellum as the seat of 

 the muscular sense. 



[Extirpation in Mammals. The dangers attending this operation are so great, that but few 

 animals survive. Luciaui, however, by using antiseptic and other precautions, has been able 

 to operate so that complete cicatrisation was obtained, the animal (young bitch) being restored 

 to health for a few mouths. The cerebellum alone was removed, but not its peduncles. As in 



