414 PATHOGENIC MICROORGANISMS 



cattle, horses, goats, cats, and dogs, are relatively refractory. Al- 

 most complete immunity toward streptococcus infections prevails 

 among birds. 



The nature of the lesions following experimental animal inocula- 

 tion 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, differ- 

 ing 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. Subcu- 

 taneous inoculation of mice may result in general sepsis followed 

 by death within thirty-six to forty-eight hours, or less, with, the 

 presence of streptococci in the heart's blood and the viscera. Intra- 

 pleural or intraperitoneal inoculation of susceptible animals with 

 virulent streptococci leads usually to a peculiarly hemorrhagic form 

 of exudate, due both to the diapedesis caused by the violent inflam- 

 matory process, and to the hemolysis of the red cells by the strepto- 

 coccic 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. 40 Marbaix 41 

 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. 



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 

 membranes, 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. 42 



Spontaneous streptococcus disease seems to occur among some 

 of the larger domestic animals. 



Fehlciscn, loc. cit.; Franlccl, Cent. f. Bakt., vi. 

 Marbaix, La Cellule, 1892. 



, Zeit. f. Hyg., ui; Hiss, Jour, Mod, Res., xix, 1908. 



