. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 29-1 MAUSUPIALIA. hut the optic thalami (t, t, fig. 117) are im- mediately brought into view, and instead of a. Phascolomys fusca. broad corpus callosum, we perceive, situated deeply at the bottom of the longitudinal Hssure, a small commisstiral medullary band, (>n, Jig. 117) passing in an arched form over the anterior part of the thalami, and extending beneath the overlapping internal or mesial sur- faces of the hemispheres, (q, Jig. 117,) which are thus, as in the Bird, disconnected with each other. On gently raisin
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 29-1 MAUSUPIALIA. hut the optic thalami (t, t, fig. 117) are im- mediately brought into view, and instead of a. Phascolomys fusca. broad corpus callosum, we perceive, situated deeply at the bottom of the longitudinal Hssure, a small commisstiral medullary band, (>n, Jig. 117) passing in an arched form over the anterior part of the thalami, and extending beneath the overlapping internal or mesial sur- faces of the hemispheres, (q, Jig. 117,) which are thus, as in the Bird, disconnected with each other. On gently raising the hemispheres from above the commissure and pressing them out- wards with the handle of a scalpel, the instru- ment passes into the fissure upon which the hippocampus (n,Jtg. 117) is folded; and, on continuing the pressure, the hippocampus is torn through, and the lateral ventricle is ex- posed. The mesial wall of the hemisphere is continued from the superior and internal border of the hippocampus, and is composed in the Wombat, as in the Bird, of a thin lamina of medullary substance analogous to a detached layer of the septum lucidum. In the Kan- garoo the mesial parietes of the lateral ventricles are stronger, being about two lines in thickness. The posterior transverse fibres of the com- missure are continued outwards and backwards beneath the more longitudinal fibres, which overlap them as they pass from the trenice hippocampi (o, fig. 117) forwards to the anterior cerebral lobes. All the fibres of the commissure pass along the floor of the lateral ventricles into the substance of the hippocampi majores, which are of proportionally very large size. Thus the commissure, which is brought into view on divaricating the cerebral hemi- spheres in the Wombat, is seen to be partly the bond of union of the two hippocampi majores in the transverse direction, and partly of the hippocampus and anterior lobe of the same hemisphere in the longitudinal direction. It ;-o fulfi
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