Buckmaster's Elements of animal physiology / by John Angell.

  • Angell, John
Date:
1866
Catalogue details

Licence: Public Domain Mark

Credit: Buckmaster's Elements of animal physiology / by John Angell. Source: Wellcome Collection.

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    their interior; they are lined with the arachnoid mem- brane, and their surfaces are moistened by a thin serous fluid'. Among other uses they subserve, they permit of the passage of bloodvessels to and from the interior of the brain. The brain is invested by three membranes—i, the pia ?nater or inner membrane, which is immediately in contact with it; 2, a middle membrane, the arachnoid membrane; and 3, an outer membrane, termed the dura mater^ which lines the interior of the skull, and forms certain canals or venous smuses for the circula- tion of the blood in the cranial cavity. The human brain weighs about 50 ounces; that of the horse about 19 ounces; the elephant, 130 to 160 ounces; and that of the whale about 80 ounces. The Cerebrum, or Brain Proper, consists of two large, similar, and equal ovoid masses, termed hemispheres, separated by a long, deep thedian groove, termed the great longitudinal fissure, which passes from front to the back of the brain. A crescent- shaped fold of the dura mater, termed the falcx, dips into the bottom of this fissure, forming a septum, which helps still further to separate the he7nispheres and to retain them in their respective situations. Each hemisphere is divided by anatomists into three lobes, viz., the anterior lobe, which is bounded on the under surface of the brain by the fissure of Sylvius; the posterior lobe, which covers the cerebellu^n; and a middle lobe, which is situated behveen the fisswe of Sylvius and the lobe overlying the cerebelhmi. The surface of the cerebrum is also broken by a number of irregular fissures or sulci of various depths. The irregular folds of brain bounded by these fissures are termed convolutions. The peculiar arrangement of these sulci and convolutions, or gyri, give the brain a folded up appearance, as shown in the diagram (see