EE NER VSS have 
THE BRAIN AND SPINAL CORD, WITH THEIR MENINGES. 
By D. J. CUNNINGHAM. 
THE nervous system connects the various parts of the body with each other and 
co-ordinates them into one harmonious whole. Its relatively great bulk and its 
extreme complexity constitute two of the most distinctive structural features 
of man. It consists of two parts, viz. the cerebrospinal nervous system and the 
sympathetic nervous system. 
The sympathetic nervous system is composed of a chain of serially disposed 
gangha, bound to each other by intervening nervous cords, and placed one on either 
side of the vertebral column. In addition to these gangliated cords, the sympathetic 
system includes certain dense plexuses of nerves and numerous scattered ganglia. 
The whole is most intimately connected with the cerebrospinal nervous sy stem, and 
both have apparently a common developmental origin. The separation of the 
nervous system into the two leading subdivisions of sympathetic and cerebro- 
spinal is therefore of a somewhat arbitrary kind. 
The cerebrospinal nervous system consists of the brain, which very nearly 
completely fills the cranial cavity, and the spinal cord or spinal marrow, which only 
partially fills the vertebral canal. These are continuous with each other, and together 
constitute the cerebrospinal axis. Attached to the brain and spinal cord are the 
humerous nerves which bring the various parts of the body into connexion with the 
central nervous axis. There are thirty-one pairs of symmetrically disposed spinal 
nerves attached to each side of the spinal cord. Each of these nerves is connected 
to the side of the cord by a ventral or anterior and a dorsal or posterior root, and 
the dorsal root is distinguished by presenting a distinct oval swelling, termed a 
spinal ganglion, on that part of its course immediately internal to the place where 
the two roots unite to form the spinal nerve-trunk (Fig. 316, p. 422 
The cranial nerves are twelve in number, but one only (viz. the fifth or tri- 
geminal) presents a double-rooted attachment similar to a spinal nerve. Several, 
however, possess ganglia in every respect comparable with the ganglia on the dorsal 
roots of the spinal nerves. These are the fifth or trigeminal, the seventh. or facial, 
the eighth or auditory, the ninth or glosso-phary ngeal, and the tenth or vagus 
cranial nerves. 
CEREBROSPINAL NERVOUS SYSTEM. 
The brain and spinal cord are composed of two substances which present a 
different appearance to the eye, and which, consequently, are distinguished by the 
terms white matter and gray matter. The difference in colour between these two sub- 
stances depends not only upon the different elements which enter into their formation, 
but also upon the fact that the gray matter is the more vascular of the two. The 
white matter is chiefly composed of nerve-fibres, whilst the essential constituents 
of the gray matter are nerve-cells which give origin to nerve-fibres. The elements 
which constitute nervous tissue are nerve-cells, nerve-fibres, and neuroglia. 
Nerve-fibres.—Nerve-fibres arranged in bundles of greater or less bulk form 
