394 



SPINAL MARROW. 



CHAPTER XIII. 



OF THE SPINAL MARROW. 



The medulla oblongata is continued from the cavity of the 

 cranium, through the great foramen of the occipital bone, into 

 the great canal of the spine ; when it takes the name of Medulla 

 Spinalis or Sjjinal Marrow. 



The dura mater passes with it through the great foramen, 

 and encloses the whole of it. At the commencement of the 

 spinal canal this membrane is attached to the surrounding 

 bones ; viz. to the margin of the great occipital foramen, and 

 to the atlas ; but below this it is loosely connected by a mem- 

 brane which sometimes appears to contain a little adeps. The 

 tunica arachnoidea and the pia mater also invest the medulla 

 spinalis. The arachnoidea appears unconnected with the 

 dura mater ; and it can easily be removed from the pia 

 mater. The pia mater adheres rather firmly to the substance it 

 encloses. 



The spinal marrow consists of medullary matter externally, 

 and cineritious or cortical matter internally. 



The fissures which are observable, anteriorly, and posteriorly, 

 in the medulla oblongata, are continued down the spinal mar- 

 row ; dividing it partially into two lateral portions : these fissures 

 penetrate to a considerable depth. Each of the lateral portions 

 is marked on its external surface, by a more superficial fissure, 

 which partially divides it into an anterior and posterior part ; 

 so that a transverse section of the spine has a cruciform ap- 

 pearance. 



The nerves go off in fasciculi from the anterior and poste- 

 rior surfaces of each lateral portion of the spinal marrow ; so 

 that each nerve is formed of two fasciculi : one from before, 

 and the other from behind. The fasciculi are of different sizes 

 in different parts of the spine. The lowermost of the neck are 





