608 PHYSIOLOGY OF THE BRAIN-STEM 



These effects gradually became compensated more or less completely, and 

 in certain cases to such an extent that one could scarcely distinguish the 

 animal from a normal one. We shall discuss this form of compensation 

 presently. 



Mere division of the cerebellum into a right and left half by a median longi- 

 tudinal section is entirely without effect (Russell). 



Complete removal of, say, the right side of the cerebellum produces, imme- 

 diately after the operation, rotation about the long axis of the animal from 

 left to right (seen from the dog's back), squinting of the eyes to the left, 

 nystagmus (to-and-fro movements of both eyes from side to side), spiral 

 twisting of the spinal column or at least of the neck region, curvature of the 

 spine with concavity to the right, tonic extension of the fore leg and at times 

 of the hind leg on the same side. 



When these effects have passed off, we observe again, as the permanent 

 effects, the complex of symptoms described as asthenia, atonia and astasia. 

 The muscles of the operated side are the ones chiefly affected, and the dis- 

 turbance is so great that for more than a month animals can neither stand 

 up nor walk without support. Later compensation develops so that the equi- 

 librium is preserved both in walking and in swimming. And yet for some 

 months after the operation numerous effects due directly to the absence of 

 the part removed are clearly perceptible. 



In man many cases of rather extensive destruction of the cerebellum have 

 been described in which no permanent effects were to be observed. This 

 agrees very well with the observation made on animals, that one part of the 

 cerebellum can take over the work of another part removed. 



When the defect is more extensive the most prominent symptoms are simi- 

 lar to those observed in animal experiments, namely, incoordination of loco- 

 motor movements', such as: unsteadiness of gait, loss of equilibrium, swaying 

 movements, etc. In light cases the patient may manage to stand, with the 

 legs wide apart, quite steadily, but in severe cases the body sways in spite 

 of strong abduction. With the feet and legs close together, flexor and extensor 

 movements of the metatarsi and of the toes are kept up, the whole body sway- 

 ing to and fro until the patient may lose his balance entirely and fall over. 

 When he walks he keeps his legs wide apart and his toes first flexed and then 

 extended; sometimes he walks on his heels, sometimes tips forward on his 

 toes ; he sometimes bends his knees, sometimes presses them far back or keeps 

 them straight; the feet are only slightly lifted from the ground; the body 

 totters and reels from one side to the other in short, the patient walks like 

 a drunken person and not infrequently falls to the ground. In some cases 

 the patient cannot even walk with support, whereas lying on his back he can 

 move his legs perfectly and can tell exactly, without looking, where a leg is 

 can in fact place one leg in a position exactly like that in which the other 

 has been placed for him; hence his motor sense is not impaired. In many 

 cases the anterior extremities are entirely unaffected, so that the patient can 

 make the most precise movements with his hands. 



Another very frequent symptom in diseases of the cerebellum is vertigo, 

 which however may be entirely wanting when the incoordination is very 



