viii THE HIND-BRAIN 433 



incomplete bilateral or unilateral, symmetrical or unsymmetrical 

 injuries, the dynamic phenomena are more irregular, both in their 

 nature and extent. In all cases the dynamic phenomena approxi- 

 mate more nearly to those of unilateral or total extirpation, 

 according as the peduncles of one side, or those of both, were 

 similarly affected. 



The immediate dynamic symptoms persist for a few days 

 usually eight to ten if the wound remains aseptic ; the tonic 

 spasms diminish in strength and duration, and become transformed 

 into clonic and oscillatory movements. 



The first symptom to disappear is the rotation 011 the long 

 axis, or tendency to fall and topple backwards (which usually 

 lasts only four to five days). The last to disappear is the pleuro- 

 thotonus or opisthotonus, which remain evident for a number of 

 days if the animal is suspended. 



As the tonic spasm disappears and the movements become 

 merely clonic and tremulous, the animal's attempts to hold itself 

 upright and to walk gradually become more effective. Dogs, as 

 a rule, regain the power of floating and swimming before they 

 become able to walk. 



In monkeys, with the exception that there is tonic flexion of 

 the fore-limbs instead of tonic extension, the dynamic symptoms 

 are identical with those described in dogs; but they are less 

 intense and of shorter duration, so that the phenomena of cerebellar 

 deficiency are more plainly seen after a very few days, when every 

 trace of the forced movements disappears. 



The exact interpretation of the origin and nature of the 

 dynamic phenomena is one of the most difficult problems we meet 

 in the physiological study of the cerebellum, and is so far unsolved. 

 The feature which has more especially claimed the attention of 

 experimenters from Pourfour du Petit (1710), Lafargue (1838), 

 Magendie (1839), Schiff (1849), Longet (1878), to the workers of 

 the present day is the rotation of the animal on its own longitudinal 

 axis. Does this depend on the irritation of the fibres of the 

 cerebellar peduncles by the operative injury or on the sudden 

 removal of the influence of one-half of the cerebellum upon the 

 rest of the nervous system ? 



In our Monograph upon the Cerebellum we declared for the 

 former view, which was already held by Brown-Sequard, Vulpian, 

 Weir-Mitchell, and others, and characterised as irritative all the 

 dynamic symptoms that predominate immediately after removal 

 of portions of the cerebellum, as Goltz had given the name of 

 inhibitory to those which ensue directly on cerebral ablation. 

 This view is supported by the following arguments : 



() They correspond with the degree of operative injury and 

 with the appearance of inflammatory and infective processes in the 

 wound. 



VOL. in 2 F 



