THE CENTRAL NERVOUS SYSTEM. 



303 



inent at higher levels, is the continuation of fibres from the anterior 

 ground-bundle of the cord. 



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. 





IM^vl^M 



Section through human cerebral peduncles at point of emergence of 

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

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

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

 motor fibres f 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 



