74 MASTITIS OF THE COW 



In dextrose media the bacillus pyogenes produces acid 

 but no gas. The media can then contain 1.3 per cent, nor- 

 mal acid. In maltose, lactose, and saccharose media it 

 forms neither acid nor gas. 



Resistancy. — The bacillus pyogenes is very sensitive. 

 Usually daylight can kill it in culture in a few days. It 

 can be kept for two months in cultures not exposed to the 

 light and sealed to preserve moisture. 



Pathogenicity. — B. pyogenes is a typical pus pro- 

 ducer and induces its effect slowly. Therefore it does not 

 cause an acute but a chronic infection. It causes suppura- 

 tive foci at the point of inoculation. The animals never die 

 of bactersemia. 



Mice manifest a subacute infection usually with no 

 alterations. One mouse, however, showed a chronic sup- 

 purative wound at the point of infection fourteen days after 

 inoculation. 



Dogs frequently but not always present a subacute 

 infection after about fourteen days and show abscesses con- 

 taining thick yellow pus and numerous pyogenes bacilli. 

 Upon intraperitoneal inoculation similar abscesses are pro- 

 duced in the omentum and mesentery. Otherwise the 

 health of the animal does not appear to be disturbed. 



Two guinea-jyigs infected subcutaneously manifested 

 no alterations after two months. 



Cows. — 1. About six months after calving a cow was 

 injected in one teat with 12 c.c. of a three-day-old bouillon 

 culture of bacillus pyogenes which had been isolated from 

 a case of calf pneumonia. This bacillus had been grown 

 on culture media for a period of three weeks. The dog 

 used as a control developed a distinct abscess at the point 

 of injection fourteen days after inoculation. 



Examination of the quarter and its milk before the in- 

 fection revealed no pathological alterations. 



The day after infection the body temperature was nor- 



