54 PROF. OWEN ON THE ANATOMY OF THE INDIAN RHINOCEROS. 
The relative longitudinal extent of the great commissure or ‘corpus callosum’ is 
shown at s, s, in the view of the vertical section of the brain of the female Rhinoceros 
given in Pl. XXII. fig. 1. A septum lucidum, q, of moderate extent, connects the under 
surface of the anterior half of the corpus callosum with the fornix: in the same section 
the optic thalami are seen at 0; the ‘plexus choroides’ at p; and the mass of the 
quadrigeminal bodies at k. The arrangement of the grey and white matter in the lobes 
and lobules of the cerebellum, forming the ‘ arbor vit,’ a, is also shown: this is less 
complex than in the Horse. 
The lateral ventricle is laid open by the removal of its outer wall to show the size 
and shape of the great hippocampus at n, fig. 2, Pl. XXII.; and in the same figure are 
shown the ‘ plexus choroides ’ p, passing through the ‘ foramen Monroianuin ’ m, beneath 
the crura of the fornix and the outer lamina of the septum lucidum, q. The left lateral 
ventricle is laid open from above to show the proportions of the ‘corpus striatum’ f, 
with the hippocampus 7, and the intervening part of the fornix, covering the optic tha- 
lamus h, together with the ‘ plexus choroides’ p. In Pl. XXI. the corpus callosum s, s, 
has been bisected and the hemispheres divaricated to show the forms and proportions 
of the bigeminal bodies ; of which the posterior pair b are broader but shorter than 
the anterior ones a. The pineal gland is shown at n; the optic thalamus at /; the 
‘plexus choroides’ at p; and the ‘ corpus striatum’ at f. 
The commencing decomposition of the inner substance of the brain prevented the 
better definition of some of the other parts of this organ. 
The common anastomotic trunk of the basilar or vertebral arteries, after traversing 
the median line of the pons, gives off a pair of arteries at right angles, which cross the 
crura cerebri between the pons and the third pair of nerves: a second pair of transverse 
branches is sent off just anterior to the former, and receive the anastomosing longitu- 
dinal branches from the ento-carotids which complete the circle of Willis. From the 
ento-carotid parts of the circle, a branch is given off to the interspace between the 
_middle and anterior lobes of the cerebrum, where it divides into three or four branches. 
The eyeballs are of small comparative size; each measured in antero-posterior 
diameter one inch five lines, and in transverse diameter one inch three lines. Some 
dark-brown pigment lies under the conjunctiva for the extent of about a line from the 
circumference of the cornea: the same kind of pigment is also deposited upon the 
outside of the nictitating eyelid, and over a great part of the inner surface of the same 
part, covered of course by a reflection of the conjunctiva. The trunks of the venz 
vorticosz perforate the sclerotica half-way between the entry of the optic nerve and 
the edge of the cornea. I injected one of these veins with mercury, which immediately 
returned by vessels perforating the sclerotica near the optic nerve. The disposition of 
the venz vorticose, with the flocculent but somewhat firm connecting tissue of their 
radiating branches, presented that structure which most nearly resembled the figures 
given by Mr. Thomas of the parts he describes as ‘‘ processes having a muscular 
