Title: The cat : an introduction to the study of backboned animals, especially mammals
Identifier: catintroduction00miva (find matches)
Year: 1881 (1880s)
Authors: Mivart, St. George Jackson, 1827-1900
Subjects: Cats; Anatomy, Comparative
Publisher: New York : Scribner's
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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2C6 THE CAT. (CHAP. IX. outer wall or bag of the cerebrum enclosing the lateral ventricles. Filling up the interval between the corpus callosum and fornix is a double membrane called the septum lucidum, a space called the fifth ventricle being included between its two layers. Below the fornix we have evidently cut into a cavity extending down into the infundibulum and bounded in front by the lamina terminalis. This cavity is called the third ventricle. A small aperture (the foramen of Monro) opens immediately behind the
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Fig. 129.—The Brain, as seen when a vertical longitudinal section has been MADE THROUGH ITS MIDDLE. etc. Anterior commissure. av. Arbor vitse of cerebellum. c. Crucial sulcus. cm. Corpus albicans. cc. Corpus callosum. cq. Corpora quadrigemina. F. Frontal lobe of cerebrum. /. Fornix. fm. Foramen of Monro (between the fornix and the corpus callosum is the fifth ventricle, enclosed by the two vertical layers of the septum lucidum, which pass from the lornix to the corpus callosum). Ji. Hippocampal gyrus. riii. Medulla oblongata. ol. Olfactory lobe. pv. Pons Varolii. p. Pineal gland. pt. Pituitary body. s. Superior external gyrus. v. Velum interpositum (between it and the fornix is a space enclosed by the folding over of the cerebrum upon the roof of the third ventricle). 3. Third ventricle. 4. Anterior end of fourth ventricle. II. Optic nerve, which leads back to the fourth ventricle beneath the cerebellum. The large white spot above Fig. 3 is the middle, or soft commissure, cut across. The white spot beneath and in front of Fig. 3 is the cut surface of the optic chiasma. anterior part of the fornix, and a little behind this aperture is the cut edge of a bundle of transverse fibres which form what is called the soft (or middle) commissure. The third ventricle is bounded above by a delicate membrane, the velum interpositum, which consists only of the ependyma, the pia mater, and the arachnoid. Its margins are very vascular, and bear the name of the choroid plexuses. The vascularity is continued on in that part of the ependyma which passes through the foramen of Monro into the lateral ventricles, but of course the pia mater and arachnoid do not pass through that foramen, as they never get inside the ventricles at all, but are reflected back on the under surface of the fornix. Thus the " choroid plexuses " of the lateral ventricles are (like those of the third) merely portions of the ependyma, which happen to be very vascular, and are not really intrusions from without. 1 his velum interpositum thickens behind and forms a small prominence which projects backwards as the pineal gland—reminding us of the pituitary body below. It is reddish and very vascular, and contains two or

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