. A dictionary of birds . y have been expected) condi-tion of the base of the bill shewn in the figure of that part in theSatin-bird. BRACHIAL ARTERY, see Vascular System : BRACHIALPLEXUS, see Nervous System. BRAIN, the part of the Central Nervous System which isenclosed by the cranium, and in Birds consists of three principaldivisions, named after their position—Hind- Mid- and hindbrain is composed of the medulla oblongata, the direct andcomparatively little modified continuation of the spinal cord, and ofthe cerebellum, these two parts being connected with each otherby the pedu
. A dictionary of birds . y have been expected) condi-tion of the base of the bill shewn in the figure of that part in theSatin-bird. BRACHIAL ARTERY, see Vascular System : BRACHIALPLEXUS, see Nervous System. BRAIN, the part of the Central Nervous System which isenclosed by the cranium, and in Birds consists of three principaldivisions, named after their position—Hind- Mid- and hindbrain is composed of the medulla oblongata, the direct andcomparatively little modified continuation of the spinal cord, and ofthe cerebellum, these two parts being connected with each otherby the pedunculi or crura cerebelli. The midbrain contains thepeduncles of the great or forebrain, and the cortex or rind of theoptic lobes. The forebrain is subdivided into the thalamencephalonand into the cerebral hemispheres. The ventral parts of thethalamencephalon form the hypophysis and the chiasma orcrossing of the optic nerves, the lateral parts contain the innerportions of the optic lobes, which are partly homologous with. 52 BRAIN hem^ the corpora bigemina of Mammals, and the optic thalami; thedorsal roof forms the epiphysis or pineal gland, the corpus callosumand the anterior commissure, both of which consist of bundles ofAvhite nerve fibres and connect the right with the left ventral portion of the hemispheres consists of the corporastriata, which are masses of grey brain-substance, and of the olfactorylobes, which mark the anterior end of the brain. The central canal, which runs through the spinal cord, is con-tinued into the brain, and forms the fourth ventricle in the hind-brain, extending dorsally into the cerebellum; and is then continuedas aquseductus Sylvii through the midbrain, with lateral exten-sions into the optic lobes. The dilatation of this canal in thethalamencephalon is the third ventricle: it extends ventrallytowards the hypophysis as the infundibulum, in a similar way Vertical section in themiddle line through THE BRAIN OF A DuCK. Enlarged. (
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Keywords: ., bookauthorlyde, bookcentury1800, bookdecade1890, booksubjectbirds
