390 PATHOGENIC MICROORGANISMS 



considerable susceptibility. Guinea-pigs possess a relatively higher 

 resistance. 17 



Subcutaneous or intramuscular inoculation of a susceptible 

 animal usually results in the formation of a localized abscess with 

 much pus formation and eventual recovery. Intraperitoneal inocula- 

 tion is more often fatal. Intravenous inoculation of doses of 0.5 

 c.c., or more, of fresh broth cultures of virulent staphylococci usually 

 leads to pyemia with the production of secondary abscesses, located 

 chiefly in the kidneys and the heart and voluntary muscles, but not 

 infrequently in other organs as well. In the kidney they occur as 

 small foci, situated most often in the cortex, composed of a central, 

 necrotic pus cavity, surrounded by a zone of acute inflammatory 

 exudation. Staphylococcus lesions form histologically the typical 

 " acute abscess." Not infrequently the pyemic condition is accom- 

 panied by suppurative lesions in the joints. Intravenous injections 

 of virulent staphylococci preceded by injury to a bone is often 

 followed by the development of osteomyelitis. Mechanical or chem- 

 ical injury of the heart valves preceding intravascular staphylo- 

 coccus inoculation may result in localization of the infection on or 

 about the heart valves, leading to "malignant endocarditis." In 

 producing experimental lesions in rabbits all varieties of staphylo- 

 coccus infection may be obtained by suitable methods of injection. 

 If, for instance, a rabbit is given one-half to 1 c.c. of a young broth 

 culture, from which the clumps have been gently centrifuged down, 

 into the ear vein, a rapid fatal septicemia will result with organisms 

 in the heart's blood, but no secondary localization or abscess forma- 

 tion. If, however, Staphylococcus cultures containing clumps are 

 gently centrifuged, the supernatant fluid taken off, and small clumps 

 injected in not too large amounts (and the amounts must be adjusted 

 to the virulence of the culture) the animal will pass through a 

 protracted illness, with secondary abscess formation in kidneys, 

 liver and other organs, in which emboli have been formed, a condi- 

 tion simulating accurately pyemia in human beings. The pyemic 

 conditions following Staphylococcus inoculation usually lead to 

 chronic emaciation and death after an interval dependent upon the 

 relative virulence of the microorganism, the amount injected, and the 

 resistance of the infected subject. 



17 Terin, Kef. in Lubarsch und Ostertag, Ergebnisse, 1896 ; Lingelsheim, 

 Aetiol. d. Staph. Inf.," etc., Wien, 1900. 



