896 



THE NERVE SYSTEM 



more sharply cut transverse furrow. The cephalic pair, the superior quadrigeminal 

 bodies (pregemina; superior colliculi; the nates of older authors), are the larger, 

 and the pineal body rests in the flattened depression between them. The superior 

 quadrigeminal bodies are oval, their long diameter being directed, cephalolaterad, 

 and are of a yellowish-gray color. The inferior quadrigeminal bodies (postgemina; 

 colliculi inferiores; the testes of older authors) are hemispherical in form and 

 lighter in color than the preceding. The lamina quadrigemina, comprising the 

 whole of the dorsal wall of the mid-brain, extends from the root region (posterior 

 commissure) of the pineal body to the cephalic end of the superior medullary 

 velum. 



FRENULUM 

 TROCHLEAR NERVE 



SUPERIOR MEDULLAR 

 VELUM (CUT) 



RESTIFORM BODY 



CUNEATE TUBERCLE 

 TUBERCULUM CINEREUM 



TAENIA PONTIS 

 TRIGEMINAL NERVE 



FACIAL NERVE 

 ACOUSTIC NERVE 

 GLOSSOPHARYNGEAL 



AND VAGUS NERVES 

 HYPOGLOSSAL NERVE 



SPINAL ACCESSORY 

 NERVE 



FIG. 659. The brain stem, showing medulla oblongata, pons, mid-brain, and part of the optic thalami. 



Each superior and inferior quadrigeminal body is continued lateroventrad in 

 prominent white bands, the brachia. The band from the superior quadrigeminal 

 body is termed the superior brachium or prebrachium; that from the inferior quad- 

 rigeminal body is called the inferior brachium or postbrachium. 



The superior brachium or prebrachium (brachium quadrigeminum superius) 

 proceeds cephaloventrad between the overhanging pulvinar and a light-gray 

 eminence, the internal geniculate body. In reality it is a continuation of a part 

 of the optic tract. The inferior brachium or postbrachium (brachium quadrigem- 

 inum inferius) proceeds in a similar direction to disappear beneath the internal 

 geniculate body. 



Of the two geniculate bodies, on either side, the external geniculate body belongs 

 rather to the thalamus (p. 906), while the internal geniculate body may properly 

 be considered here among the structures of the mid-brain. 



The internal geniculate body or postgeniculum (corpus geniculatum mediale 

 s. internals) is a small oval eminence of the lateral surface of the mid-brain in 

 which the mesal root of the optic tract appears to terminate. The inferior, 



