THE-CENTRAL NERVOUS SYSTEM. 
Goll. 
or column of Burdach. 
The membranes of the spinal cord : 
337 
The lateral and thicker is the fasciculus cuneatus (¢) 
The dura mater is a tough fibrous membrane directly con- 
tinuous with the dura mater of the brain. It 
differs from the dura mater of the brain in 
two particulars: 
I. «At the foramen magnum it splits into 
two layers, one of which lines the bony 
vertebral canal and forms its periosteum, 
while the other covers the cord. 
2. It is separated from the cord by a con- 
siderable space. The dura mater is contin- 
uous with the fibrous sheaths of the spinal 
nerves at their points of exit. Along the 
sides of the cord it is connected to the pia 
mater by a delicate strand of connective tissue 
probably equivalent to the ‘‘ligamentum 
denticulatum ’’ of man. 
The arachnoid is a delicate cellular mem- 
Fic. 134. — CrRoss- 
SECTION OF THE 
SPINAL CORD IN 
THE CERVICAL RE- 
GION. 
a, posterior median 
sulcus; 46, posterior 
lateral sulcus; ¢, an- 
terior median fissure; 
@, fasciculus gracilis; 
e, fasciculus cuneatus; 
J, white matter; g, 
gray matter; 4, cen- 
tral canal. 
brane lying beneath the dura mater, between it and the pia 
mater. It forms a continuous investment for the cord, is not 
vascular, and is said not to dip into the fissures of the cord. 
The pia mater invests the cord closely and contains some 
blood-vessels. It is a delicate membrane which dips into the 
fissures and sulci of the cord and is con- 
nected to it by numerous strands of con- 
nective tissue that pass from it into the 
substance of the cord. The nerves pierce 
it. 
Spinal Nerves.—From the spinal cord 
arise the spinal nerves. Of these there 
are about thirty-eight pairs in the cat. 
tral root. Eight are cervical, thirteen thoracic, 
seven lumbar, three sacral, and seven or eight caudal. Those 
leaving the cervical (Fig. 133, 58 and /) and lumbar (Fig. 
136) enlargements are larger than the others. The first 
cervical nerve leaves the vertebral canal through the atlantal 
Fic. 135.— SECTION OF 
+ SPINAL CORD, SHOWING 
THE ORIGIN OF A PAIR 
OF SPINAL NERVES. 
a, dorsal root; 4, spinal 
ganglion; ¢, dorsal ramus; 
d, ventral ramus ; ¢, ven- 
