X 



376 CEREBELLUM. 



The Pneumogastric lobule (flocculus) is situated on the anterior 

 border of the cerebellum, near to the origin of the eighth pair of 

 nerves, and is hence called pneumogastric. It is not unlike a con- 

 voluted shell in its form. 



The Tonsils and uvula resemble those organs in a swollen state 

 very strikingly ; they project from the under surface of the cere- 

 bellum into the fourth ventricle. 



The Lingueita laminosa i$ a thin tonguelet of gray substance, 

 marked by transverse furrows, which extend forwards upon the 

 valve of Vieussens from the gray substance of the cerebellum. 



When cut into vertically, the cerebellum presents the appearance 

 termed arbor vitcs. If the incision be made through the outer third 

 of the organ, a gray body, surrounded by a yellow zigzag line of 

 horny structure, will be seen in the centre of the white substance : 

 this is the corpus rhomboideum, or ganglion of the cerebellum. 



The cerebellum is associated with the spinal cord and cerebrum 

 by three pairs of peduncles ; the 



Corpora restiformia, 

 Processus e cerebello ad testes, 

 Crura cerebelli. 



The Corpora restiformia, or inferior peduncles, diverge at the 

 upper extremity of the medulla oblongata, and enter the cerebellum, 

 forming, by their divergence, part of the lateral boundaries of the 

 fourth ventricle. Their fibres surround the corpus rhomboideum, 

 and are expanded into the lamellae of the cerebellum. 



The Processus e cerebello ad testes are the superior peduncles : 

 they ascend from the corpus rhomboideum, on each side, to the 

 testis, and also form a part of the lateral boundaries of the fourth 

 ventricle. The valve of Vieussens, by connecting the two pro- 

 cessus e cerebello ad testes from side to side, and the cerebellum 

 and testes from behind forwards, also contributes to the antero-pos- 

 terior communication of the cerebellum. 



The Crura cerebelli are the terminations of the transverse fibres 

 of the pons Varolii, or great commissure of the cerebellum, which 

 serves to establish a transverse communication between the lateral 

 lobes. 



BASE OF THE BRAIN. 



The student should now prepare to study the base of the brain : 

 for this purpose the organ should be turned upon its incised surface; 

 and if the dissection have hitherto been conducted with care, he 

 will find the base perfectly uninjured. The arachnoid membrane, 

 some parts of the pia mater, and the circle of Willis, must be care- 

 fully cleared away in order to expose all the structures. These he 

 will find arranged in the following order from before back- 

 wards : 



