. Anthropology. which—called the olfactory bulb—lies longi-tudinally in a depression on the surface of the anterior lobe; thesecond are the optic, whose decussation at the median hne is calledthe chiasma. When we place the encephalon on its upper or convex surface,and remove the cerebeUum and pons varolii by a transverse sectionpassing between the junction of the latter with the cerebralpeduncles, the whole inferior surface of the two hemispheres isexposed to view (Fig. 15). At the junction of the anterior thirdwith the posterior two-thirds is seen a deep transverse fissure,with its concavity
. Anthropology. which—called the olfactory bulb—lies longi-tudinally in a depression on the surface of the anterior lobe; thesecond are the optic, whose decussation at the median hne is calledthe chiasma. When we place the encephalon on its upper or convex surface,and remove the cerebeUum and pons varolii by a transverse sectionpassing between the junction of the latter with the cerebralpeduncles, the whole inferior surface of the two hemispheres isexposed to view (Fig. 15). At the junction of the anterior thirdwith the posterior two-thirds is seen a deep transverse fissure,with its concavity looking backwards. This is the fissure ofSylvius (A, Fig. 16). The portion in front is the inferior surfaceof the frontal or anterior lobe; that behind is the inferior surfaceof the posterior lobe, which is separated into two weU-marked Chap. III.] EXTEENAL SURFACE OF HEMISPHERES. 103 and tmequal portions, the one with its convexity looking for-wards and outwards, which is the inferior region of the temporo-. Fig. 15,—Inferior surface of tlie encephalon: A, Anterior or frontal lobe ; B, Temporo-sphenoidal portion of the posterior lobe : A and B are separated by a fissure with itsconcavity looking backwards—the fissure of Sylvius. C 6, Cerebellum ; M, Sectionof the spinal cord where it joins the medulla oblongata ; VI, Annular protuberance—at its anterior border are seen the two cerebral peduncles ; C C, Corpus callosum—the dotted line is on the median or inter-hemispherical Hne; I to XII, The twelvepairs of encephalic nerves at their origin ; I, Olfactory nerve with its bulb ; II, Opticnerve, the union of which with that of the opposite side forms the chiasma; III,IV, VI, Nerves of motion of the globe of the eye ; V, Trigeminal, or fifth, supply-ing the m,uscles of expression; XII, Hypoglossal nerve, the nerve of motion of thetongue. Sphenoidal lobe, the other, posterior or concave, upon which thecerehellum lies. The superior or convex surface of the hemispheres may
Size: 1442px × 1733px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookpubl, booksubjecthumanbeings
