PATHOGENIC BACTERIA. 287 



minute red pimple with a hair in the center. The pimple pres- 

 ently becomes a pustule. The process may cease at this point, 

 or it may be only the commencement of a large carbuncle with 

 a central slough. Such infection has been produced experi- 

 mentally on the human skin by rubbing in cultures of Staphy- 

 lococcus pyogenes aureus. It is, furthermore, the constant 

 experience of post-mortem examiners that infection may occur 

 around the hair-follicles when no wound of the skin has been 

 inflicted. 



In many instances, infection with the pyogenic bacteria 

 follows upon some preexisting infection; this happens, for in- 

 stance, in tuberculosis, when tuberculous lungs become in 

 fected with Streptococcus pyogenes, leading to the formation 

 of a cavity. Secondary infection with pyogenic bacteria is 

 frequently due to the Streptococcus pyogenes, often also to the 

 Micrococcus lanceolatus. 



Sometimes it is impossible to detect the point of entrance of 

 pyogenic organisms. In view of the observation that tubercle 

 bacilli pass through the uninjured mucosa without leaving 

 any local lesion, but setting up the disease in places remote 

 from the point of entrance, it may be surmised that the pyo- 

 genic organisms may enter the body without leaving any crace 

 of their point of entry. 



The severe general symptoms, familiar to every physician, 

 often accompanying acute suppuration, indicate the formation 

 of toxic bacterial products and their absorption. Experimen- 

 tal evidence of the formation of such toxic products is not so 

 clear, however, for the pyogenic organisms as for some of the 

 other bacteria. It has been shown that cultures of Staphy- 

 lococcus pyogenes aureus, in which the bacteria have been 

 killed, are capable of producing suppuration in the lower 

 animals. 



The pyogenic bacteria play a somewhat different part in 

 producing disease, which is fully as important as the typical 



