212 



ANATOMY FOR NURSES. [CHAP. XVIII. 



the brain being built upon the cord, and together they form the 

 great nerve-centre or axis the cerebro-spinal which, by means 

 of the cranial and spinal nerves, is placed in 

 connection with all parts of the body. Al- 

 though the gray matter in the spinal cord 

 is intimately connected with the gray matter 

 in the brain, it has some functions indepen- 

 dent of the brain, which will be described in 

 connection with the spinal nerves. 



The spinal nerves. There are thirty-one 

 pairs of spinal nerves, arranged in the follow- 

 ing groups, and named from the regions 

 through which they pass. They are : 



Cervical 8 pairs 



Dorsal 12 " 



Lumbar 5 " 



Sacral 5 " 



Coccygeal 1 pair 



The spinal nerves pass out of the spinal 

 canal through the intervertebral foramina, 

 the openings between the vertebree spoken 

 of in the lesson on the bones of the spine. 



Each spinal nerve has two roots, an anterior 

 root and a posterior root. The fibres con- 

 nected with these two roots are collected into 

 one bundle, and form one nerve just before 

 leaving the canal through the intervertebral 

 openings. Before joining to form a common 

 trunk, the fibres connected with the posterior 

 root present an enlargement, this enlargement 

 being due to a ganglion, or small nerve 

 centre. The fibres of the anterior root arise 



nal cervical nerves; f rom t fo gray matter [ n the anterior COH1U, 



FIG. 122. BASE OF 

 BRAIN, SPINAL CORD, 

 AND SPINAL NERVES. 

 V, IX, cranial nerves; 

 a, 6, c, d, sympathetic 

 ganglia; C'M, spi- 



Di-12, spinal dorsal 

 nerves; Z,*-5, spinal 

 lumbar nerves ; S M 

 sacral ; 6, coccygeal. 



and appear for the most part to be direct pro- 

 longations from the nerve-cells there. The 

 fibres of the posterior root, on the other 

 hand, appear to arise in most cases from the cells in the ganglion, 

 and to grow into the nerve-centres forming the gray matter in the 

 posterior cornu. The fibres growing from the anterior root are 



