MENINGITIS SPINALIS. 293 



We must regard as remains of chronic inflammation :>f the arach- 

 uoid, milky opacities of that membrane, and cartilaginous or bony 

 plates, about the size of a millet-seed, which have a rough inner and 

 smooth outer surface, and which are generally very numerous, espe- 

 cially in the lower portion of the spinal cord. 



Inflammation of the pia mater is usually very extensive. In the 

 acute form we find the pia mater injected, swollen, and relaxed. In 

 the subarachnoid space there is a copious, purulent, flocculent exuda- 

 tion, or else the pia mater and arachnoid are covered with membranous 

 deposits. The spinal medulla is usually pale and bloodless ; rarely it 

 is injected, relaxed, or softened. Most cases of so-called hydrorhachis 

 acquisita appear to be due to chronic inflammation of the pia mater. 

 We spoke of opacities and oedema of the cerebral membranes as very 

 frequent post-mortem appearances in topers, and referred them to a 

 chronic meningitis ; it is also probable that inflammatory disturbance 

 of nutrition of the meninges induces the collections of large amounts 

 of fluid in the subarachnoid space of the spine, when they do not de- 

 pend on general dropsy or atrophy of the spinal marrow (in which 

 case they are unimportant, and do not cause any symptoms). More- 

 over, it is difficult to decide, from the tension of the dura mater before 

 it is incised, or by estimating the amount of liquid that escapes after 

 it is incised, whether the amount of subarachnoid fluid is abnormally 

 increased. The more cloudy or bloody the escaping fluid, the more 

 probable it is that the hydrorhachis is due to chronic inflammation of 

 the meninges. 



SYMPTOMS AND COURSE. Inflammation of the dura mater is not 

 accompanied by very prominent or characteristic symptoms when it 

 does not lead to perforation, and, by escape of pus into the subarach- 

 noid space of the spine, induce diffuse meningitis. When patients, 

 who have had an injury of the back, or have caries of the spine, com- 

 plain of pain in the back, it is, difficult to decide whether it is due to 

 inflammation of the dura mater or of the bones and ligaments. 



The symptoms of chronic inflammation of the arachnoid, and during 

 the formation of the little plates above described, are perfectly ob- 

 scure. 



Acute inflammation of the pia mater is accompanied by symptoms 

 of severe irritation in the parts supplied by spinal nerves, which are 

 subsequently generally followed by symptoms of paralysis ; it is usu- 

 ally distinctly characterized and readily recognized by these symptoms 

 and their sequence. Occasionally after a chill there is fever, and the 

 patients complain of severe pain in the back, which becomes insup- 

 portable on motion, and usually on pressure over the spine. It is 

 oHinarilv accompanied by pains in the extremities. Both the pain in 



