280 BACTERIOLOGY. 



The results that follow upon the inoculation of ani- 

 mals with cultures of streptococci obtained from various 

 inflammatory lesions are, as a rule, inconstant. At 

 times cultures will be encountered that are apparently 

 without virulence, no matter how tested ; while again 

 cultures from other sources exhibit the most marked 

 pathogenic properties, even when employed in almost 

 infinitesimal quantities. Between these extremes every 

 gradation may be expected. The virulence of a culture 

 is not necessarily proportional to the intensity of the 

 pathological process from which it is derived. 



There is never any certainty of faithfully repro- 

 ducing, by inoculation into susceptible animals, the 

 pathological lesion from which a culture of the organ- 

 ism may have been obtained. The introduction into a 

 susceptible animal of a culture derived from either a 

 spreading phlegmon or an erysipelatous inflammation 

 may result in erysipelas, general septicaBmia, local ab- 

 scess-formation, or, as said, may have no effect at all. 

 Cultures may be encountered that are pathogenic for 

 one susceptible species of animals and not for another. 



Under the ordinary conditions of artificial cultiva- 

 tion fully virulent varieties of streptococcus pyogencs 

 usually lose their virulence after a short time. 

 Petruschky 1 preserves this property by cultivation 

 upon nutrient gelatin for two days at 22 C., keeping 

 the cultures after this time in the refrigerator, and 

 transplanting upon fresh gelatin every five or six days. 

 Marmorek 2 finds the virulence preserved by growing 

 the organism in a mixture of 2 parts of horse or 



1 Petruschky : Centralblatt fur Bakteriologie und Parasitenkunde, 

 1895, Abth. i. Bd. xvii. 



2 Marmorek : Annales de 1'Institut Pasteur, 1895. 



