354 PRINCIPLES OF VETERINARY SCIENCE 



developed by Pasteur. It consists in two subcutaneous injec- 

 tions of vaccine, prepared from attenuated cultures of the bacillus 

 of anthrax, given at an interval of twelve or fourteen days. The 

 inoculations must be repeated each year to keep the immunity 

 of the animal at a point sufficiently high to withstand natural 

 infections. 



The blood-serum of animals rendered hyperimmune to anthrax 

 has been used both as a prophylactic and therapeutic agent. 

 When used in conjunction with the vaccine the chances for per- 

 fect immunity without loss are greatly increased. 



Infected herds should be quarantined, infected animals isolated, 

 and all milk or other products withheld from sale until danger 

 from disseminating the disease by them is past. 



BLACKLEG 



Blackleg is a highly contagious disease affecting cattle between 

 the ages of six and twenty-four months. It is readily com- 

 municated from animal to animal and is usually fatal after a 

 course of twelve to thirty-six hours. The period of incubation 

 is three to five days. 



Cause. — An organism known as the blackleg bacillus is the 

 sole cause. This agent gains entrance into the body through 

 abrasions of the skin. It is a gas-producing organism that 

 develops only in the absence of oxygen; therefore the wound in 

 the skin must be small, otherwise enough oxygen is admitted to 

 prevent the germ from multiplying. The source of the infection 

 is another animal sick or dead from the disease. The mode of 

 transmission is by direct contact with cases or articles freshly 

 contaminated with discharges. 



Symptoms. — The first symptoms are high fever, loss of appe- 

 tite, suspension of cud chewing, and great depression. Respi- 

 rations increase, the movements become stiff and painful, and 

 the visible mucous membranes dark red to purple in color. The 

 most characteristic symptom is the appearance of swellings over 

 the heavily muscled parts of the body such as the thighs and 

 shoulders. These swellings are at first small but increase rapidly 

 in size and may cover a large portion of the body. When 

 the skin over one of these swellings is stroked with the palm of 

 the hand a distinct crackling is heard and felt. This is due to 



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