THE NERVOUS SYSTEM. 765 



Barely, serum accumulates between the layers of the new membrane- 

 and in this way cysts of large size may be formed. In rare cases diffuse 

 suppuration of the entire new membrane occurs. 



The slighter degrees of this form of inflammation may occasion no 

 symptoms during life. They are not infrequently found in persons suf- 

 fering from various chronic brain lesions and from chronic alcoholism, 

 but they may occur unassociated with complicating lesions. The more 

 advanced forms of the lesion are frequently found in idiots, epileptics, 

 etc. 



Tuberculous pachymeningitis may occur secondarily to that form of in- 

 flammation in the pia mater or the bones, or as a part of general iniliary 

 tuberculosis. The tubercles may be situated on either surface of the 

 membrane or in its substance, and may be single or aggregated, forming 

 large masses. 



Syphilitic pachymeningitis manifests itself by the formation of so-called 

 gummy tumors upon either the external or internal surface of the dura 

 mater. These tumors may be single or multiple, and vary greatly in 

 size. They may be accompanied by simple inflammatory changes in the 

 dura mater in their vicinity. They may undergo suppuration with the 

 formation of abscess. The inflammation may extend to the pia mater, 

 inducing simple or syphilitic meningitis and adhesions between the dura 

 mater and pia mater. The gummata may, on the other hand, when occur- 

 ring on the outer surface of the membrane, cause absorption and perfo- 

 ration of the bones of the skull. 



TUMORS. 



Fibromata and Lipomata occur rarely in the dura mater and are of 

 small size. 



Small Chondromata are sometimes found connected with the dura 

 mater at the base of the brain. 



Osteomata. In addition to the formation of osteophytes in chronic 

 external pachymeningitis, plates and, more rarely, globular masses of 

 bone may be formed in the dura mater, unconnected with the bones 

 of the skull. They are most frequently found in the falx cerebri, but 

 may occur elsewhere. The new bone may be dense or loose in texture, 

 and usually produces no symptoms. 



Endotheliomata. 1 These tumors may grow inward or outward, causing 

 pressure on the brain or absorption and perforation of the bones ; they 

 often attain considerable size. Some of these tumors somewhat resemble 

 certain forms of epithelioma, and have often been described as primary 

 carcinomata. 



Sarcomata are the most common tumors of the dura mater, and of 

 these the spindle-celled forms are of more, the round- and polyhedral- 

 celled of less frequent occurrence. They -may grow from either surface 



1 For a consideration of tumors of the dura mater allied to the endotheliomata con- 

 sult Dagonet, Arch, de Med. exp., May 1st, 1892. 



