12 Anatomy of the Nervous System 



ventral surface of the hindbrain — the pons (pons X^arolii). 

 Immediately behind this (PI. II.) is another, much less dis- 

 tinct transverse band, the trapezoid body. This shows at 

 each side of the middle line a marked elevation, which is the 

 anterior end of a distinct ridge, the pyramid, extending along 

 each side of the ventral median sulcus from the lower end 

 of the medulla oblongata up to this point, where the sulcus 

 itself is obliterated by the transverse fibres. 



Coming back to the dorsal surface, the large fourth 

 ventricle or rhomboid fossa may now be studied (PI. III.). 

 This cavity narrows anteriorly into the aqueduct of Sylvius, 

 the cavity of the midbrain, and posteriorly into the central 

 canal of the spinal cord. A narrow deep posterior median 

 sulcus runs along the floor of the ventricle in the middle 

 line, and for about half the length of the ventricle a narrow, 

 low ridge, the funiculus teres, bounds this fissure at either 

 side. Just in front of this ridge the floor of the ventricle 

 forms a considerable eminence at each side, under which 

 lies the genu of the facial nerve (p. 48) and which is conse- 

 quently called the colliculus facialis. In front of this, a very 

 slight pit at each side of the ventricle is the fovea superior. 

 On a level with the funiculus teres appears a pair of large 

 rounded lateral elevations, which contain the vestibular 

 nuclei. The slight lateral pit at the posterior end of this 

 eminence is the fovea inferior. The triangular formation at 

 the posterior extremity of the ventricle is the calamus scrip- 

 torius. 



The medial parts of the dorsal columns of the spinal cord 

 (funiculi graciles) end in a pair of enlargements, the clavae, 

 which are spread apart by the ventricle, and in front of each 

 of these the thick wall lateral to the vestibular nucleus is 

 formed by the restiform body or inferior cerebellar peduncle. 

 In the cut surface of the peduncles, this body, the middle 

 peduncle or brachium pontis, and the superior peduncle or 

 brachium conjunctivum can all be distinguished. The last 



