lo Feb., 1912.] 



Diseases of Farm Animals. 



it is significant that the age period of tlie disease is synchronous with denti- 

 tion changes, and it is likely that in the great majority of cases the inocu- 

 lation occurs through the raw edges of the gums when the milk teeth are 

 being cast. Pasturing on sciub or on spear grass or other rough herbage 

 is also likely for obvious reasons to predispose to the contracting of the 

 disease. 



Lack of vigour through high condition on the one hand or through 

 poverty on the other is a noticeable auxiliary cause, as also are chills 

 and sudden changes of weather during the spring when young stock are 

 shedding their winter hair. 



Symptoms. — The period of incubation or time elapsing from inocula- 

 tion to the manifestation of symptoms varies from one to five days, the 

 average being two days. The animal then becomes dull, feverish and 

 depressed ; there is loss of appetite and rumination, and a marked increase 

 of temperature. A stiffness or lameness in walking is then ob.served. 

 This is usually confined to one limb and there quickly succeeds a 

 swelling or tumefaction of the 



affected limb or of some other part ^^^^^ ^ 



of the body. The swelling is 

 small at first but extends very 

 rapidly and may acquire a con- 

 siderable size in a few hours. It 

 is hot and painful, and when 

 rubbed or pressed with the hand a 

 crackling noise is heard due to the 

 distension of the tissues beneath 

 the skin with gas. Later, the 

 swelling becomes cold and insensi- 

 tive, and on being lanced a dark- 

 red frothy and offensive fluid 

 exudes along with bubbles of gas. 

 As the disease advances the animal 

 rapidly weakens, the breathing be- 

 comes very distressful and, pre- 

 ceded by a rapid fall of temperature, death results in from one to three 

 days. 



Post-mortem Examination. — The carcase — the internal organs as well 

 as the tissues underlying the skin — will be found greatly bloated or dis- 

 tended with gas. The tissues in the region of the swelling are engorged 

 with dark, frothy blood ; they are friable, breaking down readily under 

 finger pressure and have a bruised pulpy appearance. The bacillus is 

 present in this pulpy mass in large numbers. The lymphatic glands in 

 the neighbourhood are enlarged and congested. The lungs, liver and 

 kidneys are also usually congested but the spleen is rarely enlarged. 



Prevention. — RecoA-ery practically never occurs and curative treat- 

 ment is useless so that quick destruction of all cases definitely diagnosed 

 as blackleg is a wise procedure. The carcases should be burnt and the 

 disinfection methods and other preventive measures recommended in 

 anthrax cases and for infected areas should be carried out in every 

 detail. Cultivation of infected land is more successful in eradicating 

 blackleg than anthrax, the aeration of the soil effected by the cultivation 

 operations being inimical to the development of the anaerobic germ. 



A. Bacillus of blackleg. 



B. Bacillus of blackleg showing drumstick 



development. 



