BACILLUS COLI COMMUNIS 211 



enormously increased by growing it alternately (a) in a mixture 

 of human blood serum and bouillon (vide p. 42), and (6) in 

 the body of a rabbit ; ultimately, after several passages it pos- 

 sesses a super-virulent character, so that even an extremely 

 minute dose introduced into the tissues of a rabbit produces 

 rapid septicaemia, with death in a few hours. It has been 

 proved by Marmorek's experiments, and those of others, that 

 the same species of streptococcus may produce at one time 

 merely a passing local redness, at another a local suppuration, 

 at another a spreading erysipelatous condition, or again a 

 general septicsemic infection, according as its virulence is 

 artificially increased. Such experiments are of extreme import- 

 ance as explaining to some extent the great diversity of lesions 

 in the human subject with which streptococci are associated. 



Bacillus Coli Communis. The virulence of this organism 

 also varies much, and can be increased by passage from animal 

 to animal. Injection into the serous cavities of rabbits pro- 

 duces a fibrinous inflammation which becomes purulent if the 

 animal lives sufficiently long. If, however, the virulence of the 

 organism be of a high order, death takes place before suppura- 

 tion is established, and there is a septicaemic condition, the 

 organisms occurring in large numbers in the blood. Intravenous 

 injection of a few drops of a virulent bouillon culture usually 

 produces a rapid septicaemia with scattered haemorrhages in 

 various organs. 



Lesions in the Human Subject. The following statement 

 may be made with regard to the occurrence of the chief organisms 

 mentioned, in the various suppurative and inflammatory con- 

 ditions in the human subject. The account is, however, by no 

 means exhaustive, as clinical bacteriology has shown that practi- 

 cally every part of the body may be the site of a lesion produced 

 by the pyogenic bacteria. It may also be noted that acute 

 catarrhal conditions of cavities or tubes are in many cases also 

 to be ascribed to their presence. 



The stapkylococci are the most common causal agents in 

 localised abscesses, in pustules on the skin, in carbuncles, boils, 

 etc., in acute suppurative periostitis, in catarrhs of mucous 

 surfaces, in ulcerative endocarditis, and in various pyaemic 

 conditions. They may also be present in septicaemia. 



Streptococci are especially found in spreading inflammation 

 with or without suppuration ; in diffuse phlegmonous and 

 erysipelatous conditions, suppurations in serous membranes and 

 in joints (Fig. 56). They also occur in acute suppurative 

 periostitis and ulcerative endocarditis. Secondary abscesses in 



