470 PHYSIOLOGY CHAP. 



variously interpreted. In 1883 Schiff considered it to be one 

 of the essential elements which, along with asthenia, make up 

 the syndrome of cerebellar ataxy. But he rejected the hypothesis 

 that dysmetria depends on defective co-ordination, as Lewand- 

 owsky holds, nor did he regard it as an effect of the loss of the 

 inhibitory action of the cerebellum, as assumed by Budge in 

 1841 and by Wagner in 1858 ; he attributed it to irregularity in 

 the reinforcing action transmitted from the remaining portion of 

 the cerebellum to the group of muscles which come into play in 

 the different complex voluntary actions. Babinski, who accepted 

 this, called it cerebellar a-synergy. 



SchifPs view seems acceptable in cases of incomplete extirpa- 

 tion or pathological states of the cerebellum, but in cases of 

 complete extirpation of one lateral half, or of the whole cere- 

 bellum, his interpretation is not adequate. It must further be 

 added that dysmetria is not constant in all cases of cerebellar 

 lesion ; even in clinical cases it is a rare symptom. 



As already stated, it is probably due to atonia of the muscles 

 of the limbs, owing to which there is a too rapid relaxation of 

 the extensors when the flexors contract, and a too rapid relaxa- 

 tion of the flexors when the extensors contract. Lewandowsky 

 did not admit this simple explanation, according to which 

 dysmetria is a natural consequence of atonia. 



IX. We must now consider the function of the afferent im- 

 pulses that reach the cerebellum from the numerous afferent 

 paths, and the influence of those it transmits to its efferent paths. 

 These are the main 'problems on the solution of which the 

 physiology of the cerebellum has to rest. 



" One of the most striking and really fundamental facts bearing 

 on these problems, which finds confirmation both in physio- 

 logical experiment and in clinical observations, is that profound 

 alterations and absolute loss of the cerebellum do not paralyse 

 either sensation or volitional movement, although it has been 

 clearly demonstrated that this organ is related by its afferent 

 paths to the peripheral sense-organs (especially the cutaneous, 

 muscular, and labyrinthine senses), and by its efferent paths to the 

 peripheral apparatus for voluntary movements. While lesions of 

 other cerebrospinal centres result in true paralysis complete or 

 incomplete of sensation and motion, cerebellar deficiency is shown 

 in simple neuro-muscular atonia, asthenia, astasia. 



In order to explain these differences, we are naturally led to 

 make certain conjectures, which are in no way at variance with 

 anatomical facts, and which harmonise well with physiological 

 research as a whole : 



(a) That the cerebellum with its appendages constitutes a 

 small and comparatively independent system in itself, so that its 

 removal interrupts no important conducting paths, centripetal or 



