374 PRINCIPLES OF VETERINARY SCIENCE 



Diagnosis. — It is difficult to demonstrate the tubercle bacilli 

 in caseous or purulent matter by the microscope, but easy if the 

 material is inoculated into guinea pigs. A biologic test is used 

 to determine the presence of infection in living animals. It 

 consists of injecting tuberculin, a solution of the products of the 

 tubercle bacilli, into the body of the suspect. If the animal is 

 infected, a rise of temperature of more than 2°F. occurs a few 

 hours after the injection. The dose of tuberculin employed for 

 cattle is 2 c.c. per 1000 pounds of weight. 



The intradermal tuberculin test is coming into use. It consists 

 in injecting a few drops of concentrated tuberculin between the 

 outer and inner layers of the skin. In case the animal is infected, 

 a small, hard swelling, which is often surrounded by a softer 

 swelling, occurs at the point of inoculation in twenty-four to 

 ninety-six hours. The ophthalmic tuberculin test is also em- 

 ployed; it consists in instilling a few drops of the test fluid into 

 the eye. A reaction is shown by profuse lacrimation and 

 swelling of the lining membrane of the eyelids. 



The tuberculin test is recognized as a reliable method of 

 diagnosis. It is not infallible or fool-proof, but is much more 

 satisfactory than a diagnosis based entirely on a physical 

 examination. 



Treatment. — The first thing to do in dealing with herds found 

 tuberculous by the tuberculin test is to remove all affected 

 animals from the premises. If in a marketable condition they 

 should be slaughtered at an abattoir where a government in- 

 spector is stationed, so that the carcasses may be disposed of in 

 an approved manner. The open-air treatment so commonly 

 employed for man has been attempted for cattle, but the results 

 do not justify the expense. Medicinal treatment is unsatis- 

 factory. The immunization methods that have been tried are 

 impracticable. Preventive treatment consists in guarding the 

 food and drink against contamination with the germs responsible 

 for the disease. Pasteurization of skim milk, whey, and other 

 creamery by-products from skimming stations, creameries, and 

 cheese factories is an effective method of preventing the spread 

 of tuberculosis and other diseases carried by these by-products. 



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