174 SUPPURATION AND ALLIED CONDITIONS. 



purulent softening of the area occurs. The cocci may 

 reach the interior of the tubules, where they may be often 

 seen mixed with leucocytes, and in this way they reach 

 the bladder. 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, 

 however, 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 carbun- 

 cular condition which healed only after some weeks. Con- 

 firmatory experiments of this nature have been made by 

 Bockhart, Bumm, and others. 



When tested experimentally the staphylococcus pyogenes 

 albus has practically the same pathogenic effects as the 

 staphylococcus 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 one which also loses its viru- 

 lence 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, however, the virulence may be much 

 increased, and pari passu the effects of inoculation are 

 correspondingly varied. Marmorek, for example, has 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 page 53), and (^) in 

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

 possesses a supervirulent character, so that even an ex- 

 tremely minute dose introduced into the tissues of a rabbit 



