27 & Spinal Marrow. [Book IX, 



from the internal lamina of the pia mater; fo that by 

 blowing through a hole made in the arachnoides, it 

 will fwell from one end to the other like a tranfparent 

 inteftine. 



The fpinal marrow gives rife to about thirty pair of 

 nerves. Thofe which come out between the vertebi^ 

 of the neck are thinner than the reft, and are placed 

 almoft tranfverfely j as we ciefcend, we find them run- 

 ning more and more obliquely downwards, and when 

 we arrive at the fecond vertebra of the loins, the fpinal 

 marrow is fplit into numerous thread-like fibres, and 

 from its appearance is called cauda equina, or the 

 horfe's tail. The nerves which arile from the different 

 parts of the brain and fpinal marrow will be treated of 

 in a feparate chapter. 



