BRAIN. 125 
nephritis, and the contagious eruptive diseases. The inner surface is 
lined with a soft, yellow exudation made up of fibrin and pus. 
What are the changes in simple chronic pachymeningitis ? 
There may be simply a formation of new connective tissue in the 
dura, rendering it thicker and in many cases causing it to adhere to the 
cranium. Often there is formed a layer of delicate connective 
tissue containing numerous thin-walled bloodvessels. This form is - 
sometimes called pachymeningitis hemorrhagica interna. Blood may 
escape from these thin-walled vessels. The new tissue between the 
bloodvessels is made up of a homogeneous or fibrillated basement sub- 
stance containing numbers of spheroidal, spindle and branching cells. 
Sometimes there are found in these cases small calcareous concretions 
called brain sand. ° 
What is to be said concerning tubercular and syphilitic pachy- 
meningitis ? 
The changes seen are the same as have been described before under 
the head of inflammation. 
What tumors have been found in the dura mater? 
Osteomata, chondromata, jfibromata, lipomata, endotheliomata, 
sarcomata and psammomata. These latter are small pedicled 
tumors of sarcomatous material often containing particles of calcareous 
material resembling brain sand. 
Name pomne of the gross pathological conditions seen in the pia 
mater. 
The pia sometimes becomes oedematous. But the presence of fluid 
may be due tu post-mortem changes. Hemorrhage may occur in the 
substance of the membrane itself or between the pia and dura mater. 
Name the different forms of inflammation seen in the pia mater. 
Acute meningitis. 
Chronic meningitis. 
Tubercular meningitis. 
Syphilitic meningitis. 
Describe acute meningitis. 
This lesion occurs in two distinct forms, acute cellular and simple 
acute meningitis. In the former there is produced simply an increased 
number of cells similar to the cells normally present. There are no 
exudative products whatever. 
In the latter form the changes are exudative in character. There 
is an exudation of leucocytes in the pia mater and along the blood- 
