FUNCTIONS OF THE CEREBELLUM. 905 



There is no evidence that purely cerebellar lesions impair instinct 

 or intelligence. 



Eegarding sensory defects, Luciani, one of the earliest to hold that 

 sensory disturbances are caused by destruction of the Eolandic cortex, 

 finds none after ablation of the cerebellum, confirming in this respect 

 the original observations of Eolando and Flourens. Clinical obser- 

 vations, in this respect especially valuable, are accordant with their 

 views. There is, however, clearly one sensory disturbance, namely, 

 vertigo ; animals often indicate it by their actions, patients describe it. 

 It may be asked whether the vertigo is not secondary to abnormal 

 movements of the eyes, etc. It is not so, for it occurs in absence of the 

 eyeballs, and is said clinically to occur sometimes apart from any obvious 

 inco-ordination. To interpret this vertigo, disturbances other than 

 cerebellar occasioning vertigo may be recalled. These include, besides 

 ocular squint, many spatial positions and movements unwonted to the 

 body : the looking from a height, the gliding over ice, sea travel, to some 

 even travel by train or the covering of one eye. Common to all these 

 conditions is the synchronous rise of perceptions of spatial relations 

 between the self and the environment which have not, or have rarely 

 before, arisen in synchronous combination. The tactual organs of the 

 soles and the muscular sense organs of limbs and trunk are originating 

 perceptions that indicate that the self is standing on the solid earth, 

 yet the eyes are at the same time originating perceptions that indicate 

 that solid earth is far away below the standing self. The combination 

 is hard to harmonise at first ; it is at least not given as innately 

 harmonised. The conflicting senses occasion the feeling of giddiness. 

 The cerebellum has paths to it from most, if not from all, afferent nerve 

 roots. But to one of these it stands associated especially closely, so 

 closely that, as its place in the neural axis implies, it may be regarded 

 as having been evolved above that root, namely, the vestibular, the 

 nerve of the semicircular canals, the sense organs furnishing data for 

 the appreciation of positions and movements of the head. Traumatic 

 like other abnormal irritations of this nerve or of the cerebellum 

 originate sensations at variance with those derived from other sources 

 contributing to the space perceptions of the moment. The move- 

 ment of the body becomes thus imperfectly adjusted to the spatial 

 requirements of the act it would perform. Giddiness also supervenes. 

 Giddiness appears a symptom of only the irritative period of cerebellar 

 lesions ; and is less marked in cerebellar than in labyrinthine or eighth 

 nerve lesions. Since with huge cerebellar defect all conscious sensation 

 may remain good, the failure of the sensorial adjustment of the body's 

 movements to outer space-relations in consequence of cerebellar lesion 

 must be ascribed to loss of impulses which regulate body-movements 

 without being on their way into or within the cerebellum elaborated to 

 conscious sensations. 



Though some degree of imperfection of the movements persists 

 long or always, the above loss of direct unconscious co-ordination 

 may in large part be compensated, it would seem, by conscious sensa- 

 tions (perceptions). The movements thus compensatorily regulated, 

 although correct, strike the observer as under constant guidance 

 by attention and wanting the natural ease of automatic consum- 

 mation. 



Clinical experience even more than experimental indicates that if 



