LESIONS IN THE HUMAN SUBJECT 211 



a spreading erysipelatous condition, or again a general septi- 

 cemic infection, according as its virulence is artificially increased. 

 Such experiments are of extreme importance 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 septiceemi'c 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 inflam- 

 matory conditions in the human subject. The account is, 

 however, by no means exhaustive, as clinical bacteriology has 

 shown that practically 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 

 mucous surfaces are in many cases also to be ascribed to their 

 presence. , 



The staphylococci are the most common causal agents in 

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

 etc., in acute suppurative periostitis ; they also occur frequently 

 in catarrhs of mucous surfaces, in ulcerative endocarditis, and in 

 various pysemic conditions. They may also be present in cases 

 of septicaemia. 



Streptococci are especially found in spreading inflammation 

 with or without suppuration ; in diffuse phlegmonous and 

 erysipelatous conditions, suppuration in serous membranes and 

 in joints (Fig. 50). They are usually to be found in gun-shot 

 wounds ; at first the " enterococcus " abounds, at a later stage 

 streptococcus pyogenes is the more common type. They also 

 occur in acute suppurative periostitis and ulcerative endocarditis. 

 Secondary abscesses in lymphatic glands and lymphangitis are 

 also, we believe, more frequently caused by streptococci than 

 staphylococci. They also produce fibrinous exudation on the 

 mucous surfaces, leading to the formation of false membrane in 

 many of the cases of non-diphtheritic inflammation of the 



