vin THE HIND-BRAIN 453 



which the cerebellum had been divided in the median line by a 

 small knife and a hook, so that a considerable part of the grey 

 matter of the vermis was destroyed. 



Tracing a represents the animal's normal gait ; four to five days 

 after the operation tracings b and c were taken, which show marked 

 al id action of both fore- and hind-limbs, in order to widen the base 

 of support, thus making it easier to maintain the equilibrium and 

 avoid falling on one side or the other. The steps are also seen to 

 be shorter in comparison with the normal; to cover the same 

 distance 10 steps were taken in a, 14 in b, 13 in c. Tracing d 

 was made one month, and tracing e two months, after the 

 operation, when the improvement in walking is evident and the 

 gait so nearly normal that no one could distinguish it without 

 comparing the tracings. 



In another bitch we excised the whole of the median lobe or 

 vermis, without, however, exposing the floor of the fourth ventricle, 

 as the uvula was left partly uninjured. Tracing b of Fig. 238, 

 taken ten days after the operation, when the dynamic phenomena 

 had not entirely ceased, shows very grave locomotor disturbances ; 

 the steps are extremely short and it was found on listening that 

 the taps of the feet on the floor occurred at irregular intervals ; 

 each fore-leg frequently crosses that of the opposite side, but the 

 hind-limbs do not cross. Owing to the strong lateral oscillations 

 of the vertebral column the direction of progression is curved, and 

 often a zigzag, and the distance between the print of each lateral 

 pair of feet varies, which produces a marked disturbance of 

 co-ordination. Two days later, when the dynamic disturbances 

 had disappeared, tracing c was taken, which shows a surprising 

 improvement in the gait, and a week later tracing d, which differs 

 little or not at all from the normal. Tracing d' with the animal 

 blindfolded was obtained on the same day, and shows how little 

 influence vision has upon the gait. A month later the gait is 

 approximately the same, as shown by tracing e. Tracing e, 

 obtained after a hypodermic injection of morphia, shows that its 

 action upon the nervous centres causes the partial reappearance 

 of the ataxic phenomena. 



All our researches lead to the important conclusion that organic 

 compensation of partial lesions is dependent on the remaining 

 portions of the cerebellum, i.e. on parts with the same functional 

 character as the part extirpated, and that compensation ensues so 

 much the faster and to a greater extent, in proportion as the part 

 destroyed is small in comparison with the portions left intact and 

 able to function. 



A valuable confirmation of this analysis of the ataxy due to 

 more or less complete extirpation of the cerebellum in dogs was 

 given by Langelaan (1907) in his admirable description of a case 

 of congenital cerebellar ataxy in a young cat, which he examined 



