482 A MANUAL OF VETERINARY PHYSIOLOGY 



served that the posterior peduncle is a second afferent path 

 to the cerebellum. 



The cerebellum is connected, as we have already seen, with 

 the mid-brain, cerebrum, medulla, and spinal cord. It is 

 doubtful whether its two halves are connected. Afferent 

 impulses may pass to the cerebrum via the cerebellum, and 

 efferent impulses from the cerebrum to the muscles may reach 

 them through the cerebellum. Afferent impulses may pass to the 

 cerebellum and efferent impulses issue from it without the inter- 

 vention of the cerebrum. 



Functions of the Cerebellum. — Our knowledge respecting the 

 uses of this organ is still very incomplete. Little more is known 

 of its functions than was first demonstrated by Flourens in his 

 classical experiments carried out over eighty years ago. He 

 regarded it as being connected with locomotion and the problem 

 of body-balance. The study of comparative anatomy lent 

 support to this theory ; it was observed how highly the cerebellum 

 was developed in birds and in swift swimming fishes with great 

 locomotive power, such as the shark. In birds the vermis of 

 the cerebellum is large and deeply folded, though its hemispheres 

 are almost wholly absent, excepting in those birds which remain 

 some time in the air and possess wings and feet of considerable 

 strength. The experiment of Flourens on the cerebellum consisted 

 in its removal in the pigeon ; as the result of the operation the 

 animal was unable to fly, stand, or feed itself. When it attempted 

 to walk, spasm of the extensor muscles of the legs occurred, and 

 it fell, struggling wildly, in a state of evident panic. There 

 was no muscular paralysis, but the pose of the body was 

 awkward, the head being drawn back and twisted. During the 

 muscular spasms the contractions led to the animal turning 

 somersaults. In course of time the violent symptoms disappeared, 

 and the animal was able to fly, but for a long time was unable 

 to perch, through spasms of the extensor muscles of the limbs. 

 When the cerebellum is sliced away, and not entirely removed, 

 the gait is rendered uncertain and staggering, and there is an 

 inability to maintain equilibrium. 



In the dog injury to one hemisphere of the cerebellum leads 

 to the animal moving in a circle or rolling towards the injured 

 side, and to a disturbance of co-ordination. The entire cere- 

 bellum, however, has been removed in the dog, and the animal 

 remained alive for many months. In these cases there are 

 muscular spasms of the head, neck, and fore-legs, weakness of 

 the hind-limbs, and when the eyes are closed standing is im- 

 possible. When the acute symptoms pass away the animal 

 is left with a deficiency of muscular tone. It is interesting to 

 note that this lesion does not prevent the dog from swimming. 

 Colin exposed the cerebellum in a draught horse, and punc- 



