I24 BACTERIOLOGICAL DIAGNOSIS. 
staphylococci form an even film like a streak of paint; 
and the tubercle bacillus does not develop. Films 
should be made from the cultures, stained and exam- 
ined. The cultural examination is of great value, but 
much can be made out by the examination of stained 
films made directly from the pus. 
FLUIDS FROM JOINTS. 
The technique of the process of withdrawing these 
fluids is exactly the same as in the case of pleurisy; the 
needle will naturally be inserted at a point where there 
is definite evidence of the presence of fluid, and where 
it lies near the surface. 
The bacteriological examination is conducted on 
exactly similar lines. A few drops of the fluid should 
be allowed to flow on to the surface of a sloped tube 
of agar, and the culture obtained after twenty-four 
hours’ incubation examined in the manner already de- 
scribed. Films should also be made directly from the 
fluid and some stained by Gram’s method and others 
by a simple stain such as carbol-thionin. 
A great number of organisms may be present; the 
streptococci, staphylococci, the pneumococcus, gono-. 
coccus, and tubercle bacillus are the most important. 
The coccus which has been described by several ob- 
servers as the cause of acute rheumatism cannot be 
considered as of diagnostic importance at present; the 
same remark applies to the bacillus which is probably 
the cause of rheumatoid arthritis. 
Streptococci are readily distinguished on microscopi- 
cal examination and may be present even if the fluid 
is perfectly clear. When they are present in a joint 
