STREPTOCOCCUS PYOGENES. 139 



genes infection : Some cases of nephritis, articular rheu- 

 matism, myelitis, and infantile paralysis. Mannaberg has 

 found it in fourteen cases of Bright' s disease (C. B. v, 93), 

 whether as primary cause is questionable. 



The streptococcus plays an important role in diphtheria, 

 scarlatina, and phthisis. It accompanies the specific cause 

 of disease, and markedly influences the disease-picture, 

 especially the course of the fever (hectic fever is strepto- 

 coccus fever) (Petruschky, Z. H. xvn, 59). 



(d) In animals : As the cause of similar diseases (com- 

 pare, for example, Strept. equi, p. 142). 



In the vaccine of cow-pox institutes it is not uncommon, 

 but usually possesses little virulence. 



Experimental Observations Regarding Pathogenic 

 Action. — With living cultures. The virulence fluctu- 

 ates greatly; even freshly isolated organisms may be very 

 faintly virulent, and virulence for experimental animals 

 does not prove virulence for man ; with cultivation upon 

 the ordinary nutrient media the virulence is rapidly lost. 

 By repeated transmission through animals, a virulence 

 which was high at first may be much intensified. Mar- 

 morek obtained cultures of such virulence that j^Vo- c. mm. 

 killed almost all, and l0 ^ 00 c.mm. some, mice when 

 given subcutaneously — i. e., quantities that contain only 

 relatively few germs. 



The virulence is well preserved, according to Marmorek, 

 upon (1) two parts of human or horse serum and one part 

 of bouillon ; (2) one part of fluid from ascites or pleural 

 exudate and two parts of bouillon, even after keeping two 

 months in the incubator without transfer to fresh nutrient 

 media. 



In general the most susceptible to the streptococcus 

 among animals are mice and rabbits; much less, dogs and 

 rats (Pansini). Streptococci are still better tolerated by 

 sheep and goats, and best by the horse and ass. 



Knorr has ascertained the folloAving principal points re- 

 garding the virulence : By repeated transmission through 

 mice an organism is obtained which is very pathogenic for 

 mice, but at the same time its virulence for rabbits was 

 gradually lost. This is a strong indication that one must 

 not found any species upon a specific virulence. The more 



