The chief function of the cerebellum appears to be the maintenance of equilibrium. Symmetrical lesions on both sides of the organ or division of it down the centre from before backwards, cause very little disturbance of the equilibrium, but when a lesion is unsymmetrical the equilibrium is disordered.

According to Ferrier, if the lesion affects the whole of a lateral lobe, there is a tendency for the animal to roll over towards the affected side. In an animal standing on all fours or lying on the ground, we regard the centre of the back as the point of movement, but in a man standing upright we usually take the face, and therefore what we should regard in an animal as rolling towards the affected side, would be equivalent in man to a rotation towards the sound side. If the lesion is limited to one part of the lateral lobe, it may not cause rotation, but only falling towards the opposite side. When the anterior part of the middle lobe of the cerebellum is injured, the animal tends to fall forward, and in walking usually stumbles, or falls on its face. When the posterior part of the middle lobe of the cerebellum is injured, the head is drawn backwards and there is a continual tendency to fall backwards when moving.1

Injuries of the cerebellum are frequently associated with a certain amount of nystagmus, and in all probability the complete or partial inability to walk or stand which alcohol produces, is due to its action on the cerebellum.

Different kinds of spirit appear to have a tendency to affect different parts of the cerebellum, for good wine or beer is said to make a man fall on his side, whisky, and especially Irish whisky, on his face, and cider or perry on his back.2 These disturbances of the equilibrium correspond exactly with those caused by injury to the lateral lobes, and to the anterior and posterior part of the middle lobe of the cerebellum respectively. Apomorphine in large doses appears also to have an action on the cerebellum or corpora quadrigemina, as the animal poisoned by it does not vomit, but moves round and round in a circle.

The action of alcohol on frogs is peculiar and differs from that of other narcotics, inasmuch as it appears to affect unequally the two sides of the nervous apparatus by which the equilibrium is maintained, so that in a certain stage of alcohol-poisoning they excite similar manege movements to those which occur after division of the corpora quadrigemina on one side.3

1 Ferrier, Functions of the Brain, p. 94. 2 Shorthouse, Baily's Magazine of Sports, 1880, vol. xxxv. p. 396. 3 Wilhelm Wundt: Untersuchungen zur Mechanik der Nerven und Nerven-centren. Zweite Abtheilung, 1876. Stuttgart.