PATHOGENIC BACTERIA. 



243 



transplantation from one medium to another; but at times 

 the diminished virulence is due to unknown causes. The 

 lower animals used for experiments are not as readily infected 

 as man. The local introduction in rabbits or guinea-pigs of 

 a part of a culture of Staphylococcus pyo- 

 genes aureus may be entirely without effect. 

 The use of a very large dose, or the addition 

 at the same time of some kind of irritant, may 

 produce an abscess. Large amounts of cul- 

 tures in bouillon may often be injected into 

 the peritoneal cavity of the dog without 

 effect, when the simultaneous addition of a 

 piece of sterile potato or an injury to the 

 gut may lead to fatal peritonitis. Intro- 

 duction of fluid cultures into the venous 

 circulation of the rabbit generally produces 

 metastatic abscesses in the kidneys, the 

 heart-muscle and the voluntary muscles, and 

 causes death. 



In man this organism produces sup- 

 puration of a localized character, such as 

 we are familiar with in boils and carbuncles. 

 It has been shown to be the usual cause of 

 infectious osteomyelitis. OsteomyeKtis has 

 been produced experimentally in rabbits by 

 the injection of the Staphylococcus pyogenes 

 aureus, both with and without previous in- 

 jury to the bone of the animal. Ulcerative 

 endocarditis has on numerous occasions 

 been shown to be due to this organism. It has been found 

 possible to produce ulcerative endocarditis experimentally in 

 animals by the injection of the Staphylococcus pyogenes aureus 

 when the valves of the heart have first been mechanically 

 injured. The Staphylococcus pyogenes aureus has also been 



Fig. 6i.' — Staphylo- 

 coccus Pyoge- 

 nes Aureus. 

 Gelatin Cul- 

 ture, One Week 

 Old. 



