THE NERVOUS SYSTEM 



13" 



Blood-supply. — The pia mater derives its arteries from (i) the 

 anterior and posterior spinal arteries, and (2) the neural branches 

 of the lateral spinal arteries. 



Nerve-supply. — ^The nerves are derived from the sympathetic 

 system. 



Structure. — The spinal pia mater consists of two layers — outer and inner. 

 The outer layer consists of fibrous tissue, which is disposed for the most part 

 in parallel longitudinal bundles. The inner layer consists of areolar tissue, 

 containing a great many bloodvessels, and its outer and inner surfaces are 

 covered by endotheUal cells. Between the two layers there are narrow cleft- 

 like lymphatic spaces, which communicate \vith the subarachnoid space, 

 and with lymphatic clefts ciround the arteries of the pia mater. 



Dora Matet 



Pia Mater 



Arachnoid 



Ligamentum Denticulatum 



Subdural Space 



Subarachnoid Space 



Septum Posdcum 



Fig. 547. — Diagram of a Transverse Section of the Spinal Cord 

 AND ITS Membranes. 



A.M.F. Anterior Median Fissure, with 



Process of Pia Mater 

 P.M.F. Posterior Median Fissure 



A.C. Anterior Column 



L.C. Lateral Column 



P.C. Posterior Column 



A.R. Anterior Nerve-Root 

 P.R. Posterior Ner\-e-Root 



G. Spinal Ganglion 

 S.P. Spinal Nerve 

 A.P.D. Anterior Primarj- Division 

 P.P.D. Posterior Primary Divbion 



The spinal pia mater differs from the cranial pia mater in being 

 thicker and more adherent to the ner\'ous matter. The greater 

 thickness is due to the presence of the outer layer, the cranial pia 

 mater representing the inner layer of the spinal pia mater.. 



Linea Splendens. — ^The pia mater presents a glistening vertical 

 fibrous band, which hes over the ventral median fissure. This 

 band is kno\\-n as the linea splendens, and it extends along the 

 entire length of the cord and along the conus medullaris on to the 

 filum terminale. 



Ligamentum Denticulatum. — This is a fibrous band which ex- 

 tends along the spinal cord, on each side, opposite the corresponding 

 lateral column. It lies between the ventral and dorsal roots of the 

 spinal nerves, and extends from the margin of the foramen magmmi 

 to the lower end of the cord. It lies within the subarachnoid space, 

 and partially divides that space into two compartments — ^ventral 

 and dorsal. 



