TRYPANOSOMES, TRYPANOSOMIASIS, AND SLEEPING SICKNESS 
79 
The leptomeninges are inflamed in varying degrees, the cellular infiltration 
being chiefly around the vessels, where it consists of a thick layer of lymphocytes ; 
some of the vessels however show no such infiltration around them. This 
infiltration is found along the vessels running in the sulci, and it is made up of 
lymphocytes, a few large mononuclears, phagocytes, with peripherally situated nuclei 
and all sorts of inclusions, a varying number of red blood corpuscles, and cells having 
the appearance of granulation tissue cells. The infiltration to a certain extent 
accompanies the vessels into the cortex itself, being usually more marked in its 
deeper portions, especially in the large grey ganglia. The perivascular space is in 
places dilated and contains transudate. 
In this case also the changes were most marked in the basal ganglia, where a very 
extensive layer of infiltration was found around nearly all the vessels. The vessels 
contain a good number of white blood cells, and in the larger arteries sometimes the 
whole wall contains blood corpuscles interpolated among its own normal constituents. 
The perivascular infiltration consists mainly of lymphocytes, a few large mono- 
nuclears, granulation tissue cells, and a few plasma cells. External to the layer of 
cells often occurs a large space filled with transuded fluid. Usually the endothelium 
of the larger vessels is normal, while that of the smaller ones is proliferated, the 
intima appearing as little projections into the lumen of the vessel. 
The infiltration extends to the brain tissue in the neighbourhood of the vessels, 
destroying it. The neuroglia is markedly proliferated in places. There are only 
a very few capillary haemorrhages. 
In the choroid plexus there are many gaps between the cells and a slight 
inflammation of the connective tissue. The cells themselves, however, show very 
little change. The pons, and medulla show the same perivascular changes as in the 
cerebrum, with occasional capillary haemorrhages. The meningitis is most 
pronounced over the cerebellum. 
The spinal cord and its membranes show the same changes as the brain. The 
pia and arachnoid are more or less infiltrated with round cells, the infiltration 
following the vessels into the substance of the cord. The pia shows a haemorrhage 
into its substance at the level of the first dorsal. The connective tissue in the pia is 
loose owing to extravasated red blood corpuscles. 
The peripheral part of the cord is oedematous, and its neuroglia proliferated. 
Around the vessels of the cord the small-celled infiltration is much more marked 
in those found in the grey substance than in the white ; groups of six to ten vessels 
sheathed in a dense layer of lymphocytes are often observed. The neuroglia is a 
little proliferated. Various sized small haemorrhages are very often found in the 
grey matter, especially in the posterior cornua, often involving them to more than 
one-third their breadth ; no blood pigment present. The nerve roots are also the 
seat of small haemorrhages. The central canal is dilated, and its epithelial cells 
