PNEUMOCOCCUS. 63 
pairs. The rest of the slide will be unstained, so that 
you will not be able to make out the capsule. 
Now examine the carbol-fuchsin specimen. You will 
see the cocci coloured a deep red, and you will also 
notice that the general surface of the film is stained 
pink, while there is a clear and colourless zone round 
each pair of cocci. This is the capsule, which is 
rendered distinct by ‘negative staining.” If the 
carbol-fuchsin has been allowed to act too long the 
capsule may be stained a faint pink. 
INTERPRETATION OF RESULTS. 
In cases of lobar pneumonia you will probably find 
pneumococci in great quantity, and no other bacteria in 
a specimen of sputum made in the manner described. If 
you find many pneumococci in a case of lobular 
pneumonia the disease may have been caused by 
another germ, and the cocci in question may have 
been nothing more than a secondary infection. The 
carbol-fuchsin specimen should be searched for bacilli 
resembling those of influenza, &c., and another should 
be stained for the tubercle bacillus if the clinical aspect 
of the case suggests the possibility of a tubercular origin 
for the disease. 
Pus is examined in the same way and presents similar 
appearances. Most of the cocci are extra-cellular. 
The method of making a film from pus is described in 
a subsequent chapter. It is very similar to that 
described above, but the upper slide should be allowed 
to fall on the lower one by its own weight; the two 
should not be pressed together. 
