PART V 



NEUROLOGY, OE THE ANATOMY OF THE 

 NERVOUS SYSTEM 



THE CEREBROSPINAL AXIS 



THE SPINAL CORD 



THE spinal cord is enclosed by three membranes, the dura, 

 arachnoid, and pia. 



The spinal dura is a loose fibrous envelope which is attached 

 closely to the margin of the foramen magnum above, but 

 only loosely to the circumference of the vertebral canal below 

 blending with the periosteum on the dorsum of the coccyx, 

 where it is called the coccygeal ligament. Its inner surface 

 is covered by a layer of epithelium, and it presents on each 

 side a series of double orifices for the exits of the anterior 

 and posterior roots of the spinal nerves. The dura is pro- 

 longed on to these nerves as a tubular investment. 



The arachnoid is a very delicate membrane which invests 

 the cord between the dura and pia. It is continuous above 

 with the cerebral arachnoid, and is connected by meshes of 

 fibrous tissue with the pia, and to some extent also with the 

 dura, from which it is separated by the subdural space. The 

 subarachnoid space contains the subarachnoid fluid, which 

 separates it from the pia mater. This space, by means of the 

 foramen of Magendie, is continuous with the cavity of the 

 ventricles of the brain. 



The pia is closely connected to the cord, and sends a pro- 

 longation down into the anterior, and a very delicate process 



