. The anatomy of the domestic animals . Veterinary anatomy. 772 NERVOUS SYSTEM OF THE HORSE various parts of the tube. In the higher animals the result is that 'the tubular character of the brain is not ^'ery evident, since the lumen comes to consist of four irregular cavities, the cerebral ventricles, which are connected by narrow passages. The tube is first subdivided by two con- strictions into tliree brain vesicles, termed respectively the hind-brain or rhombencephalon, the mid-brain or mesencephalon, and the fore-brain or prosencephalon. The hind-brain gives rise to three secondary segmen
. The anatomy of the domestic animals . Veterinary anatomy. 772 NERVOUS SYSTEM OF THE HORSE various parts of the tube. In the higher animals the result is that 'the tubular character of the brain is not ^'ery evident, since the lumen comes to consist of four irregular cavities, the cerebral ventricles, which are connected by narrow passages. The tube is first subdivided by two con- strictions into tliree brain vesicles, termed respectively the hind-brain or rhombencephalon, the mid-brain or mesencephalon, and the fore-brain or prosencephalon. The hind-brain gives rise to three secondary segments and the fore-brain to two. The annexed table indicates the origin of the principal structures of the fully developed brain from the primitive vesicles. It has become customary to describe the brain with reference to its embryological relations. Longitudinal fissure Transverse fissure. Olfactory btilb^ Frontal pole of hemisphere Cerebrum y Occipital pole of hemisphere Cerebellum Medulla, oblongata Fig. 631.âBrain of Horse; Dorsal View, About 7 Natural Size. Hardened in situ. 1, Entomarginal fissure; 2, marginal fissure; 3, ectomarginal fissure; 4> suprasylvian fissure. TABLE INDICATING THE DERIVATION OF THE PRINCIPAL BRAIN Phimart Segments. Secon'dary Segments. Derivatives. Myelencephalon Medulla oblongata I Pons \ Cerebellum, Rhombencephalon (pi terior vesiclej J INIetencephalon PARTS OF THE Cavities. - Fourth ventricle Mesencephalon (middle [ Isthmus rhombencephali . f Anterior cerebellar peduncles. \ Anterior medullary velum . , eaeucepuaiou trniuuie / ,^i j â - \ --de) Mesencephalon { g^Xd redunde?"'.:;:;;::} Cerebral aqueduct Prosencephalon rior vesicle). (ante- Optic thalami Diencephalon -j Hypothalamic tegmenta. Pineal body Pituitary body Optic nerves and retinae. Cerebral hemispheres . , . Olfactory tracts and bulb. Telencephalon. Posterior part, of third ventricle Anterior part of third ventricle. Lateral ventricles and olfac- tory Please no
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