PRODUCERS Of .\ntCESSES, CELLULITIS AXD SEPTICAEMIA 341 



titles of 20 c.c. or over, produce only a slight redness, or no reaction at 

 all, when injected subcutaneously, and little or no effect when injected 

 directly into the circulation. Many of the streptococci obtained from cases 

 of cellulitis, abscess, empyema, and septicaemia belong to this group. 



A number of varieties of streptococci have thus been discovered,, 

 differing in virulence and in their growth on artificial media; but all 

 attempts to separate them into various classes, even with the use of 

 specific serum, have largely failed, because the differences observed, 

 though often marked, are not constant, many varieties having been 

 found to lose their distinctive characteristics, and even to apparently 

 change from one class to another. A further objection to any of the 

 existing classification of streptococci, which are based on the manner 

 of growth on artificial culture media, is that it has been impossible to- 

 make any which would at the same time give even an approximate 

 idea of their virulence. Experiments have proved that streptococci 

 originally virulent may become non-virulent after long cultivation on 

 artificial media, and, again, that they may return to their original 

 properties after being passed through the bodies of susceptible animals. 

 The peculiar type of virulence which they may acquire tends to per- 

 petuate itself, at least for a considerable time. 



One important fact that experience teaches us is, that those streptococci 

 which are the most dangerous are those which have come immediately 

 from septic conditions, and the more virulent the case the more virulent 

 the streptococci are apt to be for animals of the same species. There 

 seems also to be a strong tendency for a streptococcus to produce the 

 same inflammation, when inoculated, as the one from which it was 

 obtained; for example, streptococci from erysipelas tend to produce 

 erysipelas, from septicaemia to produce septicaemia, etc. Streptococci, 

 however, obtained from different sources (abscesses, puerperal fever, 

 sepsis, erysipelas, etc.) are in many instances capable, under favorable 

 conditions, of producing erysipelas when inoculated into the ear of a 

 rabbit, as has been proved by experiment, provided they possess 

 sufficient virulence. 



OCCURRENCE ix MAN. Streptococci have been found in man as the 

 primary cause of infection in the following diseases : Erysipelas, circum- 

 scribed and extensive acute abscesses, impetigo, cellulitis (circumscrilxMl 

 as well as diffused), sepsis, puerperal infection, lymphatic abscesses, 

 angina, bronchopneumonia, periostitis, osteomyelitis, synovitis, otitis 

 media, mastoiditis, meningitis, pleurisy, 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 frequently 

 the source of deeper infection, such as abscesses and septicaemia; 'and 

 in certain cases attended with a diphtheritic exudation, in which the 

 Loeffler bacillus has not been found by competent bacteriologists, it 

 seems probable that the streptococcus pyogenes, alone or with other 



