EXPERIMENTAL INOCULATION 217 



Intravenous injection in rabbits, for example, produces in- 

 teresting results, which vary according to the quantity used. If 

 a considerable quantity be injected, the animal may die in 

 twenty-four hours of a general septicaemia, numerous cocci being 

 present in the capillaries of the various organs, often forming 

 plugs. If a smaller quantity be used, the cocci gradually dis- 

 appear from the circulating blood; some become destroyed, 

 while others settle in the capillary walls in various parts and 

 produce minute abscesses. These are most common in the 

 kidneys, where they occur both in the cortex and medulla as 

 minute yellowish areas surrounded by a zone of intense con- 

 gestion and haemorrhage. Similar small abscesses may be 

 produced in the heart wall, in the liver, under the periosteum, 

 and in the interior of bones, and occasionally in the striped 

 muscles. Very rarely indeed, in experimental injection, do 

 the cocci settle on the healthy valves of the heart. If, how- 

 ever, when the organisms are injected into the blood, there 

 be any traumatism of a valve, or of any other part of the 

 body, they show a special tendency to settle at these weakened 

 points. 



Experiments on the human subject have also proved the 

 pyogenic properties of those organisms. Garre inoculated 

 scratches near the root of his finger-nail with a pure culture, a 

 small cutaneous pustule resulting; and by rubbing a culture 

 over the skin of the forearm he caused a carbuncular condition 

 which healed only after some weeks. Confirmatory experiments 

 of this nature were made by Bockhart, Bumm, and others. 



When tested experimentally, the staphylococcus pyogenes 

 albus has practically the same pathogenic effects as the staphylo- 

 coccus aureus. 



The streptococcus pyogenes is an organism the virulence of 

 which varies much according to the diseased condition from 

 which it has been obtained, and also one which loses its virulence 

 rapidly in cultures. Even highly virulent cultures, if grown 

 under ordinary conditions, in the course of time lose practically 

 all pathogenic power. By passage from animal to animal, how- 

 ever, the virulence may be much increased, and pari passu the 

 effects of inoculation are correspondingly varied. Marmorek, 

 for example, found that the virulence of a streptococcus can be 

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

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

 body of a rabbit ; ultimately, after several passages it possesses 

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

 dose introduced into the tissues of a rabbit produces acute septi- 



