Etiology. 



41 



to 38°C., poorly at 14''C. The gelatin becomes liquefied; in 

 the depth of the agar culture medium along the needle punc- 

 ture radiating white growth devel- 

 ops (Fig. 15). The bouillon at 

 first becomes uniformly turbid, 

 small gas bubbles appearing on the 

 surface and later a white sediment 

 is formed, above which the solution 

 is clear. From dextrose and lactose 

 (not from saccharose) the bacillus 

 develops a gas which is either odor- 

 less or resembles rancid butter 

 (Preisz, Smith). Milk is curdled 

 only imperfectly. 



-^ ^ "^ _ Fig. 12. Blackleg bacilli from an 



Tenacity. Fresh blackleg meat is ster- agar culture. Flai>ella staining, 

 ilized in 2 hours at a temperature of 80 °C. or 

 in 20 minutes at 100°C. ; fresh virus inclosed in 

 glass tubes is made inactive in 2 minutes when 

 kept in hot vrater. On the other hand, in 

 dried meat, the spores are made inactive only 

 by heating to 110°C. for 6 hours, or boiling 

 in water for 2 hours, while at room tempera- 

 ture the spores in dried muscular tissue 

 are kept virulent at least 2 years (according 

 to Mattel even 10 years) ; in salted meats they 

 are kept virulent for more than 2 years, and 

 in decaying flesh 6 months. Temperature be- 

 tween 85 and 100 °C. decreases the virulence 

 of the spores through the destruction of the 

 toxins. Extreme cold has hardly any effect 

 In the summer, exposed to direct sunlight, the 

 dried virus loses its activity in 24 hours, and 

 the fresh virus in 18 hours. The spores show 

 also considerably more resistance to chemical 

 disinfectants than the bacilli. The most ef- 

 fective are carbolic acid (2%), salicylic acid 

 (1:100), nitrate of silver (1:1000), and bi- 

 chloride of mercury (1:5000); vapors of thy- 

 mol and eucalyptus weaken fresh virus, as it 

 is destroyed by the action of these media 

 in 100 hours (Arloing, Cornevin & Thomas). 

 Virus contained in blackleg meat possesses 

 a greater resistance than do cultures (A. 

 Schmidt). 



Pathogenicity. After subcu- 

 taneous or intramuscular injection 

 of larger quantities of meat juice 

 containing spores there appear in 

 the inoculated cattle, marked fever- 

 ish symptoms, and, at the place of 

 injection, a painful, warm, edema- 

 tous, and later crepitant swelling, which, after the death of the 

 animal produces a black color of the musculature of the in- 

 volved region. These muscles together with the serous 

 infiltrated subcutaneous and intramuscular tissue are found in- 

 terspersed with gas bubbles. If an animal is inoculated 

 subcutaneously, with only a small amount of the infectious sub- 



Fig. 14. Blackleg bacilli ivith 



spores. Muscle juice from a 



guinea pig; dried cover glass 



preparation ; fuchsin staining. 



