404 



PHYSIOLOGY 



Sup.Vermls 



C.R.V- 



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 charac- 

 terised 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 attempts 

 to correct the tendency to fall 

 towards the side of the lesion 

 by an exaggerated abduction 

 of the limbs to that side, and 



Schema of connections of Deiters' j s a l ways rea( Jy to take ad- 

 nucleus. (BRUCE.) f -i 



OR, restiform body; RN, roof nuclei; SF, sagittal vantage of the support of a wall 



fibres from cortex to roof nuclei ; CVT, cerebello- to enable it to maintain its 

 vestibular tract ; DN, Deiters' nucleus ; in, vi, . V1 . . . . 



nuclei of third and sixth nerves; PLF, posterior equilibrium, bwimmmg IS much 



longitudinal bundle; vm, vestibular division of better carried out than walking, 



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 

 posture of the body as a whole in relation to its environment, which is at 



FIG. 202A. 



