THE CENTRAL NERVOUS SYSTEM. 



303 



inent at higher levels, establishes important communications between 

 the nuclei of several cranial nerves. 



THE CRURA. 



The crura cerebri, or cerebral peduncles, resemble the pons 

 in general arrangement, since they consist of a ventral portion, the 

 crusta pedunculi, or the cerebral peduncle proper, made up 



FIG. 336. 



Section through human cerebral peduncles at point of emergence of 

 oculo-motor nerve : C, crusta, separated from tegmentum ( Tg) by sub- 

 stantia nigra (5) ; R, raphe dividing formatio reticularis ; F, longitudinal 

 bundles of latter ; O, groups of nerve-cells connected with origin of oculo- 

 motor fibres (Om) ; Tf, cells connected with origin of trifacial nerve ; A , 

 aqueduct of Sylvius; CQ, anterior corpora quadrigemina. (After Krause.) 



exclusively of ascending and descending fibre-tracts, and of a dorsal 

 portion, the tegmentum, which contains the prolongation of the 

 formatio reticularis and of the dorsal stratum of the gray substance 



