414 



THE NERVOUS SYSTEM. 



from the cerebral hemispheres, as for impressions carried up- 

 wards to them by the different nerves which preserve their 

 connection with the organs of the various senses. 



STRUCTURE AND PHYSIOLOGY OF THE CEREBELLUM. 



The cerebellum (7, 8, 9, 10, Fig. 147) is composed of an 

 elongated central portion called the vermiform processes, and 

 two hemispheres. Each hemisphere is connected with its fel- 

 low, not only by means of the vermiform processes, but also 

 by a bundle of fibres called the middle crus or peduncle (the 

 latter forming the greater part of the pons Varolii), while a 

 superior crus with the valve of Vieussens, connects it with the 

 cerebrum (Fig. 147, 5), and an inferior crus (formed by the 



FIG. 147. 



"* View of cerebellum in section and of fourth ventricle, with the neighboring parts 

 (from Sappey after Hirschfeld and Leveille). 1, median groove of fourth ventricle, 

 ending below in the calamus scriptorius, with the longitudinal eminences formed by 

 the fasciculi teretes, one on each side ; 2, the same groove, at the place where the 

 white streaks of the auditory nerve emerge from it to cross the floor of the ventricle ; 

 3, inferior crus or peduncle of the cerebellum, formed by the restiform body ; 4 , 

 posterior pyramid ; above this is the calamus scriptorius ; 5, superior crus of cere- 

 bellum, or processus a cerebello ad cerebrum (or ad testes) ; 6, 6, fillet to the side of 

 the cruracerebri ; 7, 7, lateral grooves of the crura cerebri ; 8, corpora quadrigemina. 



prolonged restiform body) connects it with the medulla ob- 

 longata (3, Fig. 147). 



The cerebellum is composed of white and gray matter like 



