THE SPINAL NERVES, THE CRANIAL NERVES, AND THE 
SYMPATHETIC NERVOUS SYSTEM. 
By A. M. PATERSON. 
THE SPINAL NERVES. 
The spinal nerves are arranged in pairs, of which there are usually thirty-one. 
Each nerve arises by two roots from the spinal cord, and, after leaving the spinal 
canal through the inter-vertebral foramen, is distributed to the trunk and lmbs 
by means of a series of branches in a manner to be described below. 
The spinal nerves are designated cervical, thoracic, lumbar, sacral, and coccygeal, 
in relation to the 
3 . Dorsal nerve-root 
Ver tebree betw een Pia mater ————_— ___ Ligamentum 
which they emerge Arachnoid denticulatum 
= 
Ventral nerve-root 
from the spinal canal. 
Each nerve appears 
below the correspond- 
ing vertebra, except GS 
the first of the cervical 
series, which passes 
out of the spinal canal 
between the occipital 
bone and the atlas. 
There are thus eight 
cervical nerves (the 
last appearing — be- 
tween the seventh cer- 
vical and first thoracic 
vertebre); there are 
twelve thoracic, jive 
lumbar, jive sacral, 
and one coccygeal 
nerve, all appearing 
below the correspond- 
ing vertebree. 
The thirty-first 
nerve is occasionally 
absent ; and there are 
sometimes one or two 
additional pairs of oases 
minute filaments below ~~ division 
the thirty-first, which, Anterior primary 
however, do not emerge Cavers 
from the spinal canal. Fic. 419.—ScHEME OF THE ARRANGEMENT OF THE MEMBRANES OF THE 
These are rudimentary SPINAL CORD AND THE Roots OF THE SPINAL NERVES. 
caudal nerves. 
The size of the spinal nerves varies extremely. The largest are those which take part 
in the formation of the great nerve trunks for the supply of the limbs (lower cervical and 
first thoracic, and lower lumbar and upper sacral nerves); and of these the nerves 
destined for the lower limbs are the larger. The coccygeal nerve is the smallest of the 
Dura mate? 
Dorsal nerve-root 
— Ventral nerve-root 
Ventral nerve-root 
Ligamentum 
denticulatum 
Arachnoid 
| wy Fe mater 
Dorsal nerve-root 
% 3 Dorsal ganglion 
@ Posterior primary 
division 
Anterior primary division 
Ventral nerve-root 
Spinal cord 
i 
