. Anatomy of the cat. Cats; Mammals. THE CENTR/1L NERI^OUS SYSTEM. 343 'tween-brain, in the median line, is a deep fissure, showing that here in reality is the termination of the original tube, the further extension craniad being due to the pushing forward of the lateral outgrowths, or cerebral hemispheres, which extend in ventral view a considerable distance further craniad. The hemispheres lie also caudad, laterad, and dorsad of the mid- brain and 'tween-brain, so that these parts are almost enveloped by the hemispheres. The hemispheres and 'tween-brain are sometimes taken together as formin
. Anatomy of the cat. Cats; Mammals. THE CENTR/1L NERI^OUS SYSTEM. 343 'tween-brain, in the median line, is a deep fissure, showing that here in reality is the termination of the original tube, the further extension craniad being due to the pushing forward of the lateral outgrowths, or cerebral hemispheres, which extend in ventral view a considerable distance further craniad. The hemispheres lie also caudad, laterad, and dorsad of the mid- brain and 'tween-brain, so that these parts are almost enveloped by the hemispheres. The hemispheres and 'tween-brain are sometimes taken together as forming a single portion, the fore- brain or prosencephalon. There are thus altogether five principal subdivisions of the brain, each enclosing a portion of the central cavity. These are the myelencephalon, the metencephalon (these two enclos- ing the fourth ventricle), the mesencephalon (enclosing the cerebral aqueduct), the diencephalon (enclosing the third ventricle), and the two cerebral hemispheres, con- stituting together the telencephalon, and enclosing the two lateral ven- tricles. A plan of the brain, con- sidered as a tube enclosing cavities, is given in Figs. 139 and 140. Fig. 139 shows the plan considered as 140. — Diagram of Brain from. i Fig. 139,—Diagram of Brain FROM Above. Fig. THE Side. I, myelencephalon; 2, metencephalon; 3, mesencephalon; 4. diencephalon; 5, telencephalon. <?, canal of the spinal cord; d, fourth ventricle; c, cerebral aqueduct (aqueduct of Sylvius): (/, third ventricle; ^, lateral ventricle; /, interventricular fora- men (or foramen of Monro); g, lamina terminalis; A, olfactory bulb. viewed from the dorsal side. Fig, 140 in a lateral view. These figures are of course pure diagrams, showing only what may be called the plan of structure, and omitting all details. In the actual conditions many important modifications even of the main features of the plan are met Please note that these images are extracted from scanned page images that m
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