42 Blackleg. 



stance, no edema ^\'ill, as a rule, appear at the place of injec- 

 tion itself, but at some distance a small swelling appears, which 

 disappears in a few days. If the inoculated amount has been 

 very small, the injection will only cause a small indisposition 

 and a moderate increase in temperature for a few days. 



The intravenous injection of a larger amount of virus 

 produces typical blackleg, but a smaller amount causes only 

 2 or 3 days of indisposition, indicated by trembling and an in- 

 considerable increase of temperature. A similar effect follows 

 the intratracheal injection of the virus. In animals which have 

 gone through the short indisposition, the disease cannot be 

 produced by a second injection of even a larger amount. In- 

 oculation in the tail of the animal only causes a crepitant swell- 

 ing and fever, if the tail is covered up, since its temperature, 

 which is normally 29.8° C, is thus artificially raised to 38.6° C. 



In calves less than six months old, the subcutaneous or in- 

 travenous injection of an amount of fresh and virulent virus 

 which in 90% of cases would be fatal to a grown animal (1 to 6 

 drops) only produces a slight indisposition. Larger amounts 

 of virus, 7 to 10 drops for 1 to 14 days old and 10 to 20 drops 

 for 3 to 10 weeks old calves, produce typical blackleg (Arloing, 

 Cornevin & Thomas). 



Small amounts of virus inoculated intramuscularly kill 

 guinea pigs, goats and sheep within 12 to 36 hours; mice are 

 also very susceptible, while rabbits, rats and pigeons are in- 

 fected only in exceptional cases. In horses and asses only an 

 inconsequential swelling appears after the injection; hogs are 

 slightly and other animals are not at all susceptible to the 

 infection. 



In artificial culture media both toxins and gases are produced, but 

 most abundantly in Martin's bouillon. Intravenous injection of 10 to 

 12 cc. of an old culture kills horses in 5 minutes, evidently through 

 the action of the toxin. The toxin is mostly confined to the bodies 

 of the bacteria, culture filtrates being much less effective. The toxin 

 very soon becomes inactive in the air, while heating for 10 min- 

 utes at 115°C. only weakens without destroying it (Roux) ; its nega- 

 tive chemotaxis turns positive at 75°C. (Leclainche & Vallee). 



According to Grassberger and Schattenfroh, the toxin is a product 

 of the bacilli and is particularly in evidence in the presence of car- 

 bonate of calcium. In calves 40 cc. of the filtrate of a culture cause 

 edematous swelling, fever, perspiration, diarrhea, prostration and, after 

 5 to 6 days, death. Contrary to other bacterial toxins, these show their 

 poisonous effect on the injected animal at once, without any distinct 

 period of incubation (Leclainche & Vallee, Eisenberg). 



In many cases natural infection results from the fact that 

 mud from the swampy and rough soil of certain regions pene- 

 trates under the skin of the cattle, particularly through wounds 

 on the tail and the extremities (Liipke observed the disease 

 after castration). 



More frequently the infection results from the consumption 



