126 THE NERVOUS SYSTEM. 
vessels, together with the formation of fibrin and serum. The exuda- 
tive products occur in varying proportions. 
‘What are the microscopical changes in chronic meningitis ? 
There is a thickening of the pia mater by a production of new 
connective tissue and an exudation of fibrin, pus and serum, The 
walls of the bloodvessels may be thickened. 
What are the characteristics of tubercular meningitis ? 
The tubercular inflammation is usually secondary to tubercular in- 
flammation in some other part of the body. The inflammation is 
present commonly in the form of miliary tubercules, and is especially 
liable to occur near or around a bloodvessel, which, at the same time, 
may be the seat of an obliterating endarteritis. Products due to an 
accompanying exudative inflammation are also present. 
Describe syphilitic meningitis. 
There is a formation of gumma tumors. With this process there is 
usually associated a simple exudative inflammation with the production 
of fibrin, serum and pus. 
What tumors occur in the pia mater ? 
Sarcomata, endotheliomata, jfibromata, lipomata, angiomata and 
myxomata may occur as primary growths. Carcinoma may occur as 
a secondary condition. 
Describe acute ependymitis. 
It is an exudative inflammation of the ependyma, occurring by itself 
or in connection with other inflammations of the brain. The blood- 
vessels are more prominent and the ependyma is infiltrated with pus. 
The surface of the membrane is covered with fibrin and pus, and the 
ventricles of the brain may be filled with purulent serum. 
What are the changes in chronic ependymitis ? 
The ependyma is thickened by a growth of new connective tissue 
and the ventricles of the brain may contain more serum than usual. 
What is hydrocephalus ? 
It is a condition in which the ventricles of the brain are dilated and 
contain more fluid than is normally present. This condition is often 
associated with the different forms of ependymitis. 
Name the different varieties of chronic hydrocephalus. 
Congenital hydrocephalus, which is present at or develops soon after 
birth, 
