STREPTOCOCCUS PYOGENES. 483 
rabbit, as has been proved by experiment, provided 
they possess sufficient virulence (Knorr, Petruschky). 
If the culture does not have the required virulence to 
produce this effect the virulence can usually be acquired 
by passage through animals. Streptococci obtained from 
the same disease and from the same individual usually 
show very much the same degree of virulence. 
Occurrence in Man. Streptococci have been found 
in man as the primary cause of infection in the follow- 
ing diseases: Erysipelas, acute abscesses, small and 
large, cellulitis, circumscribed as well as diffused, sep- 
sis, puerperal infection, lymphatic abscesses, angina, 
pneumonia, periostitis, otitis media, mastoiditis, men- 
ingitis, empyema, and endocarditis. Associated with 
other bacteria in diseases of which they were the specific 
cause, they have also been found as the secondary or 
mixed infection in many diseases, such as in pulmonary 
tuberculosis, bronchopneumonia, septic diphtheria, and 
diphtheritic scarlatina. In diphtheritic false membranes 
this micrococcus is very commonly present, and is fre- 
quently the source of deeper infection, such as abscesses 
and septicemia; and in certain cases attended with a 
diphtheritic exudation, in which the Léffler bacillus 
has not been found by competent bacteriologists, it 
seems probable that the streptococcus pyogenes, alone 
or with other pyogenic cocci, is responsible for the local 
inflammation and its results. These forms of so-called 
diphtheria, as first pointed out by Prudden, are most 
commonly associated with scarlatina and measles, ery- 
sipelas, and phlegmonous inflammation, or occur in in- 
dividuals exposed to these or other infectious diseases. 
So uniformly are streptococci present in the pseudo- 
membranous inflammations of patients sick with scarlet 
