402 



PHYSIOLOGY 



Sup.Vermis 



C.R:-:- 



evoked are those concerned in maintaining equilibrium and are involved in 

 every alteration in the position of the body. 



EFFECTS OF ABLATION OF THE CEREBELLUM. Complete unilateral 

 extirpation of the cerebellum, after the irritative effects of the lesion itself 

 have passed away, brings about a condition of the animal characterised by : 



(1) Slight loss of power on the same side of the body. 



(2) Considerable loss of tone on the same side. 



(3) Tremors or rhythmical 

 movements of the muscles on 

 the same side accompanying 

 any willed movements. 



These three symptoms are 

 denoted by Luciani as asthenia, 

 atonia, and astasia. At first 

 the animal -is quite unable to 

 stand, and lies on the side of 

 the lesion with neck and trunk 

 curved in the same direction ; 

 when it attempts to stand it 

 always falls to the same side. 

 After two or -three weeks the 

 power to stand is regained, 

 though when it attempts to 

 walk the hindquarters drag 

 and tremors accompany every 

 effort. The animal endeavours 

 to correct the tendency to fall 

 towards the side of the lesion 

 by an exaggerated abduction 

 of the limbs to that side, and 

 nucleus. (BRUCE.) is always ready to take ad- 



CR, rrstifnnn body ; EN, roof nuclei ; SF, sagittal vantage of the support of a 



veSLTtra^tT DX/^iters^nudeu; ^^ WaU tO ^ 1 * Jt tO maintail1 its 



nuclei of third and sixth nerves ; PLF, posterior equilibrium. Swimming is much 



longitudinal bundle; vm, vestibular division of h pH -pr Pflrri'prl rmt than walkina 

 eighth nerve ; sc, semicircular canals ; VST, vesti- 



bulo-spinal fibres. the contact of the water with the 



skin furnishing guidance to the 

 spinal mechanism which is lacking when the animal attempts to walk. 



When the whole cerebellum is removed the animal is unable to walk, 

 sometimes for months. After a time it gradually learns to walk, but this is 

 carried out by an alteration of the method of progression. The disorders of 

 locomotion are quite distinct from the spinal ataxia observed after interfer- 

 ence with the afferent tracts from the muscles. The difficulty now is that 

 each diagonal movement of the limbs in progression tends to throw the 

 centre of gravity to one side or other of the basis of support, and it is the 

 mechanism for maintaining the right position of the centre of gravity, i.e. the 



'!(}'! \. Schema of connections of Deiters' 



