NEUBOLOGY. 



THE CEREBRO-SPINAL AXIS. 



By E. A. SCHAFER. 



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.- 



-VlEW OF THE CEREBRO-SPINAL AXIS. 



Bourgery. ) i 



(After 



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 vertebraa opposite to 

 the place of their natural exit from the cranio-spinal cavity. 



F, T, 0, frontal, temporal and occipital lobes of cere- 

 brum ; C, cerebellum ; P, pens Varolii ; m o, medulla 

 oblongata ; m s, m s, point to the upper and lower 

 extremities of the spinal marrow ; c e, on the last lumbar 

 vertebral spine, marks the cauda equina ; v, the three 

 principal branches of the nervus trigeminus ; C i, the 

 sub-occipital or first cervical nerve ; C vm, the eighth or 

 lowest cervical nerve ; D i, the first dorsal nerve ; D xn, 

 the last dorsal ; L i, the first lumbar nerve ; L v, the last 

 lumbar ; S i, the first sacral nerve ; S v, the fifth ; Co I, 

 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. 



