DISSECTING MANUAL. 



each half of the central white mass are three small gray nuclei, 

 viz.: the embolus (nucleus embolif ormis) , just internal to the 

 hilum of the corpus dentatum; the nucleus globosus, internal 

 to the embolus; and the nucleus fastigii (roof nucleus), in the 

 corpus trapezoides, close to the midline. [509] 



Peduncles. All pass through the great horizontal fissure and 

 into the white core. The middle, the largest and most external, 

 come from the pons ; the superior emerge at the inner side of 

 the preceding, and cross the pons to the mid-brain; the inferior 

 emerge between the others, bend sharply and descend as the 

 restiform bodies. [510] 



Medullary Vela. These are two thin laminae, prolonged from 

 the white core, which pass through the great horizontal fissure 

 in contact, and then diverge. The superior (valve of Vieussens) 

 passes upward under the lingula, stretching between and con- 

 tinuous with the inner dorsal edges of the superior peduncles; 

 the trochlear nerves emerge from its dorsal surface near the 

 quadrigeminal bodies. The inferior, curving forward and 

 downward over the nodule, soon ends in a free and thickened 

 crescentic edge; laterally it stretches to the flocculi. [511] 



MID-BRAIN. 



This is short and narrow; it connects the cerebrum with 

 the pons and cerebellum. The corpora quadrigemina are two 

 pairs of rounded eminences, on its dorsum, separated by two 

 grooves, longitudinal and transverse; the inferior pair are the 

 smaller but better defined. A white band (inferior brachium) 

 runs, from each lower body, upward under the internal genic- 

 ulate body to, chiefly, the optic thalamus; another (superior 

 brachium), from each upper body, runs upward between the 

 thalamus and internal geniculate body to the external genic- 

 ulate body, and, slightly, lateral root of the optic tract. At 

 the upper end of the longitudinal groove is a depression for 

 the pineal body ; a white band (f renulum veli) runs from its 

 lower end to the valve of Vieussens; the transverse groove 



[32] 



