182 DE. J. MUEIE ON THE FOEM AND STEUCTUEE OF THE MANATEE. 



peduncles ; it is wide and crescentic, but moderately narrow from before back^vards, and 

 the posterior border is slightly concave. The medulla oblongata is not remarkable for 

 size ; at least, like the pons, it is not prominent superficially at the anterior pyramids («/>); 

 and these have a very shallow longitudinal median depression. The olivary and restiform 

 bodies are individually well represented, though imperfectly defined in our drawing, 

 on account of the membrane having partially been left attached to the nerve-roots. 



Of the cranial nerves I may remark that the olfactory root comes into view at the basal 

 end of the Sylvian fissure as a great, broad flattened tract. This narrows forwards and 

 then expands into a large pyriform bulb (1), which curves upwards and protrudes, as an 

 adpressed mass, against the antero-inferior surface of the frontal lobe. The optic 

 tracts (2), of moderate calibre, approach each other nearly transversely from the inner 

 borders of the so-called central lobes, and form a short, narrow commissure. The third 

 nerves (3) have a usual situation from the crural junction close to the pons. The 

 trochlear (fourth) nerve (4), a particularly fine filament, was but partially traced as it 

 wound round the right peduncle. Eelatively and absolutely the fifth (5) nerve is of enor- 

 mous size, and, as it leaves the side of the pons, appears composed of a great number of 

 funiculi; but among these I did not discriminate its sensory and motor roots. The 

 flattened nerve passes sharply outwards and pierces the dura mater at the recess beneath 

 the posterior margin of the alisphenoid transverse band, where the Casserian ganglion is 

 lodged. The sixth nerve (6) appeared large, as certainly was the facial motor branch 

 of the seventh pair (7). The glossopharyngeal and pneumogastric branches of Willis's 

 eighth pair of nerves (8), as also the hypoglossal or ninth nerve (9), issued as numerous 

 filamentous cords from the side of the medulla oblongata, and, unless from their more 

 anterior situation, undistinguishable from the spinal series. The different direction and 

 deeper situation of the spinal accessory branch (8*) of the eighth enabled it to be 

 distinguished with ease. 



The interior of the brain I examined in two sections, viz. horizontally and vertically. 

 When the lateral ventricle is exposed, as in the left hemisphere (fig. 35), it is seen to 

 be a large chamber, and altogether spacious. The anterior cornu (ac), a sweeping semi- 

 circle, is both deep and wide. The portion of the corpus striatum (cs) is a considerable 

 ovoid and prominent mass, leaving, however, a large cornual space in front. At its 

 posterior border, between it and the thalamus (fJi), the taBuia semicircularis (fs), a narrow 

 linear strip, crosses it obliquely outwards and backwards. 



The middle descending cornu (dc) is a moderate-sized cavity, with a more than usual 

 vertical curve in the usual directions. The eminence of the hippocampus major is veiy 

 proiinnent, convex, and well defined ; and continuing on to almost the tip of the tem- 

 poral lobe, it forms a not very distinctly notched pes hippocampi. A narrow fillet in 

 front I took to be a corpus fimbriatum. There is an undoubted postei'ior cornu (jJc), a 

 fully developed hippocampus minor, and an eminence I am inclined to recognize as 

 eminentia coUateralis. 



