Topographical anatomy of the dog / by O. Charnock Bradley.

  • Orlando Charnock Bradley
Date:
1927
Catalogue details

Licence: In copyright

Credit: Topographical anatomy of the dog / by O. Charnock Bradley. Source: Wellcome Collection.

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    Numerous small olfactory nerves leave the olfactory bulb and immediately enter the foramina of the ethmoid bone. They are usually left behind when the brain is removed. The optic nerve is a large round cord leaving the optic chiasma. The oculomotor nerve has origin from the cerebral peduncle about the middle of its length and towards its medial border. Since the origin of the trochlear nerve is from the anterior medullary velum, it cannot be demonstrated at present. The nerve itself, however, will be found curving round the lateral border of the cerebral peduncle, in the interval between this and the cerebrum and cerebellum. The trochlear is the smallest of the cerebral nerves. The trigenmial nerve is the largest of the cerebral group and arises by two roots from the lateral part of the pons. Of the roots, the larger (portio major) is sensory in function ; while the much smaller medial root (portio minor) is motor. The abducent nerve has its origin from the most anterior part of the groove forming the lateral limit of the pyramid of the medulla oblongata. The facial and acoustic fierves arise together from the lateral extremity of the corpus trapezoideum. The facial is the more medial, and slightly the smaller. From the lateral border of the ventral surface of the medulla, a series of nerve rootlets take origin. These join to form the glosso-phaiyngeal, vagus^ and accessory 7ierves. The accessory nerve, in addition to its medullary roots, contains fibres derived from the cervical part of the spinal cord. These unite to form a single cord that enters the cranium by the foramen magnum and joins the medullary roots to form the complete nerve. The hypoglossal nerve arises by several rootlets from the posterior part of the groove lateral to the pyramid. Dissection.—As a preliminary to the examination of the surface of the cerebral hemispheres, they must be carefully denuded of the covering formed by the pia mater and arachnoid. Since the whole of their surface cannot be examined without the separation of the two hemispheres from each other, two brains should be procured if possible. One of these should be left intact ; while the cerebellum, medulla oblongata, and pons of the other should be separated from the cerebrum by a transverse incision made just in front of the pons. The two hemispheres of this specimen may now be isolated by an incision in the plane of the great longitudinal fissure. The Cerebral Hemispheres {Heniisphceria cerebri).—The two cerebral hemispheres form the greater part of the bulk of the brain. Each is flattened laterally in a varydng degree, and may be described as having three surfaces—dorso-lateral, mmdial, and ventral—though there is no definite line of distinction between the dorso-lateral and ventral surfaces. The dorso-lateral surface, for the most part convex, is applied to the walls of the cranium. The medial surface is flattened, and much of it faces the corre¬ sponding surface of the opposite hemisphere: the most posterior