THE CEREBELLUM. 



623 



THE CEREBELLUM. 



It is not necessary in order to comprehend the uses of the cerebel- 

 lum, as far as these are known, to enter into a full description of its 

 anatomical characters. The points, in this connection, that are most im- 

 portant are the following : the division of the substance of the cerebellum 

 into gray and white matter; the connection between the cells and the 

 fibres ; the connection of the fibres with the cerebrum and with the prolon- 

 gations of the columns of the spinal cord ; the passage of fibres between the 

 two lateral lobes. These are the only anatomical points that will be con- 

 sidered. 



Physiological Anatomy. The cerebellum, situated beneath the posterior 

 lobes of the cerebrum, weighs about 5-25 ounces (148-8 grammes) in the male, 

 and 4*7 ounces (135 grammes) in the female. The proportionate weight to 

 that of the cerebrum is as 1 to 8f in the male, and as 1 to 8 in the female. 

 The cerebellum is separated from the cerebrum by a strong process of the 

 dura mater, called the tentorium. Like the cerebrum, the cerebellum pre- 

 sents an external layer of gray matter, the interior being formed of white, or 

 fibrous nerve-tissue. The extent of the gray substance is much increased 

 by abundant, fine convolutions and is farther extended by the penetration, 

 from the surface, of arborescent processes of gray matter. Near the centre 

 of each lateral lobe, embedded in the white substance, is an irregularly den- 

 tated mass of gray 

 matter, called the 

 corpus dentatum. 

 The convolutions 

 are finer and more 

 abundant and the 

 gray substance is 

 deeper in the cere- 

 bellum than in the 

 cerebrum. These 

 convolutions, also, 

 are present in many 

 of the inferior ani- 

 mals in which the 

 surface of the cere- 

 brum is smooth. 



The cerebellum 

 consists of two lat- 

 eral hemispheres, 



more largely developed in man than in the inferior animals, and a median 

 lobe. The hemispheres are subdivided into smaller lobes, which it is unne- 

 cessary to describe. Beneath the cerebellum, bounded in front and below by 

 the medulla oblongata and pons Varolii, laterally, by the superior peduncles, 

 and above, by the cerebellum itself, is a lozenge-shaped cavity, called the 



FIG. 230. Cerebellum and medulla oblongata (Hirschfeld). 

 1,1, corpus deiitatum ; 2, pons Varolii ; 3, section of the middle peduncle ; 

 4, 4, 4, 4, 4, 4, laminae forming the arbor vitae ; 5, 5, olivary body of the 

 medulla oblongata ; 6, anterior pyramid of the medulla oblongata ; 7, 

 upper extremity of the spinal cord. 



