QUAIN'S

ELEMENTS OF ANATOMY

EDITED BY

EDWARD ALBERT SCHÄFER, F.R.S.

PROFESSOR OF PHYSIOLOGY AND HISTOLOGY IN UNIVERSITY COLLEGE, LONDON,

BIOLOGY

LIBRARY

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BIBLIOGRAPHICAL NOTE.

Ninth Edition, 2 Vols., 8vo. November, 1882. Vol. I. Reprinted March, 1884; October, 1887. Vol. II. Reprinted December, 1883; April, 1887.

New Edition, edited by E. A. Schäfer and G. D. Thane, in 8 separately issued Parts and Appendix, 1890–6.

Vol. III., Part I. (The Spinal Cord and Brain), first separate issue, January, 1893. Reprinted August, 1895; February, 1900; September, 1900.

BRADBURY, AGNEW, & CO. LD., PRINTERS, LONDON AND TONBRIDGE.

THE CEREBRO-SPINAL AXIS.

By E. A. SCHÄFER.

THE cerebro-spinal axis is divided into the brain or encephalon, the enlarged part within the skull, and the spinal cord within the vertebral canal. It is symmetrical in form, consisting of a right and a left half, separated to some extent by fissures and cavities, but united by various portions of white and grey nervous substance which cross from one side to the other, and

Fig. 1.-VIEW OF THE CEREBRO-SPINAL AXIS. (After
Bourgery.)

The right half of the cranium and trunk of the body has been removed by a vertical section; the membranes of the right side of the brain and spinal cord have been cleared away, and the roots and first part of the fifth and twelfth cranial nerves, and of all the spinal nerves of the right side, have been dissected out and laid separately on the wall of the skull and on the several vertebræ opposite to the place of their natural exit from the cranio-spinal cavity.

F, T, O, frontal, temporal and occipital lobes of cerebrum; C, cerebellum; P, pons Varolii; m o, medulla oblongata; m s, m s, point to the upper and lower extremities of the spinal marrow; ce, on the last lumbar vertebral spine, marks the cauda equina; v, the three principal branches of the nervus trigeminus; CI, the sub-occipital or first cervical nerve; C VIII, the eighth or lowest cervical nerve; D 1, the first dorsal nerve; D XII, the last dorsal; LI, the first lumbar nerve; L v, the last lumbar; S 1, the first sacral nerve; S v, the fifth; Co 1, the coccygeal nerve; s, the left sacral plexus.

form the commissures of the brain and spinal cord.

The cerebro-spinal axis is enveloped within the skull and vertebral canal by three connective tissue membranes, between which are spaces occupied by a clear fluid (cerebro-spinal fluid). These envelopes, which will be described later, are, 1st, a firm fibrous membrane named the dura mater, which is placed most externally; 2nd, a delicate membrane called the arachnoid; and, 3rd, a highly vascular membrane named the pia mater, which is next to, and closely invests the surface of the brain and cord.

VOL. III.

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