STREPTOCOCCUS PYOGENES 341 



rats are less easily infected, and the larger domestic animals, cattle, 

 horses, goats, cats, and dogs, are extremely refractory. Almost complete 

 immunity toward streptococcus infections prevails among birds. 



The nature of the lesions following animal inoculation depends upon 

 the manner of inoculation, the size of the dose given, and most of all 

 upon the grade of virulence of the inoculated germ. Subcutaneous 

 inoculations, according to the virulence of the inoculated material, may 

 result in a simple localized abscess, differing from a staphylococcus 

 abscess only in the more serous nature of the exudate and the frequent 

 occurrence of edema, or in a severe general septicemia with a hardly 

 noticeable local lesion. Subcutaneous inoculation of mice results almost 

 invariably in general sepsis followed by death within thirty-six to forty- 

 eight hours, or less, and the presence of streptococci in the heart's blood 

 and the viscera. Intrapleural or intraperitoneal inoculation of suscep- 

 tible animals with virulent streptococci leads usually to a peculiarly 

 hemorrhagic form of exudate, due both to the diapedesis caused by the 

 violent inflammatory process, and to the hemolysis of the red cells by the 

 streptococcic hemolysins. Inoculation of rabbits at the base of the ear 

 with virulent streptococci may result in the formation of a lesion 

 indistinguishable histologically from erysipelas in man. l Marbaix 2 has 

 shown that such erysipeloid lesions could be produced in rabbits by 

 streptococci from various and indifferent sources, provided that the 

 virulence of each strain could be sufficiently enhanced. This marked 

 variability of the resulting lesion as determined by the degree of virulence 

 of the incitant, whatever its original source, forms a strong argument in 

 favor of the opinion that all the pyogenic streptococci are members of a 

 single species. 



Intravenous inoculation of rabbits with virulent cultures usually 

 results in a rapidly fatal septicemia. An animal which has died of a 

 streptococcus infection usually shows serosanguineous edema about the 

 point of inoculation, multiple hemorrhagic spots upon the serous mem- 

 branes, and congestion of the viscera. The microorganisms can almost 

 invariably be found in the heart's blood, in the spleen, and in the exudate 

 about the inoculated area. Microscopically, when the process has lasted 

 sufficiently long, parenchymatous degeneration of all the organs may be 

 observed. In the more chronic infections articular and periarticular 

 lesions may occur. 3 



1 Fehleisen, loc. cit.; Frankel, Cent. f. Bakt., vi. 



2 Marbaix, La Cellule, 1892. 



3 Schutz, Zeit. f. Hyg., iii; Hiss, Jour. Med. Res., xix, 1908. 



