776 THE XEBVOUS SYSTEM. 



THE DURA MATER SPINALIS. 



The dura mater spinalis, unlike that of the brajn, does not serve as periosteum to 

 the bones forming the cavity, so that the lesions of the two membranes differ somewhat. 



HEMORRHAGE. 



Haemorrhage may occur, as the result of injury, between the dura 

 mater and. periosteum, or it may occur in tetanus, as a result of circula- 

 tory changes induced by muscular spasm, or in the asphyxia of new- 

 born children. Small haemorrhages on the surfaces of the membrane 

 may occur as the result of inflammation. 



Serous fluid may accumulate outside of the dura mater as a result of 

 post-mortem changes, or in connection with circulatory or inflammatory 

 changes in the membranes. 



INFLAMMATION. (Pachymeningitis.) 



Acute external pachy meningitis is usually secondary to disease or in- 

 jury of the spinal column, and may result in collections of pus between 

 the dura mater and periosteum, usually most abundant posteriorly. 

 Haemorrhagic pachymeningitis occurs in the dura mater spiualis, with the 

 formation of products similar to those observed in the brain, in the 

 chronic insane and in drunkards. Simple chronic pachymeningitis interna 

 with the formation of new connective tissue containing brain sand, is not 

 infrequent. The new tissue may form minute projections from the sur- 

 face, or, when more abundant, may take the form of psammomata. Tuber- 

 culous inflammation of the dura mater spiualis may occur in connection 

 with tuberculous meningitis, or be secondary to tuberculous inflammation 

 of the vertebrae. 



TUMORS. 



Fibromata, lipomata, chondromata, myxomata, endotheliomata, and adeno- 

 sarcomata occur in the dura mater spinalis as primary tumors. Carci- 

 nomata and sarcomata may occur as secondary tumors. Small plates of 

 new-formed bone are rarely found in the dura mater spinalis. 



PARASITES. 



Echinococcus developing outside of the spinal canal may perforate the 

 dura mater ; or the cysts may lie between the dura mater and the pia 

 mater. 



THE PIA MATER SPINALIS. 



It is difficult in most cases in the pia mater, as well as in the dura mater spinalis 

 and in the spinal cord, to judge with certainty, from the appearances after death of 

 the blood contents of the vessels, of these parts during life. The same is true of abnoi- 



