378 AGRICULTURAL AND INDUSTRIAL BACTERIOLOGY 



recognized by a rise of at least one and one-half degrees 

 above the previous maximum recorded temperature. Usu- 

 ally the temperature begins to rise within 8 hours after 

 injection and reaches its maximum in 18 hours, then grad- 

 ually subsides. 



In addition to the generalized tuberculin reaction local 

 reactions are frequently used in disease diagnosis. Most 

 common of these is the so-called intradermal test used in 

 cattle. In this method a small amount of tuberculin is 

 injected into the skin (not under the skin) ; most commonly 

 this injection is made into the skin showing no hair at one 

 side of the tail. The reaction consists of a circumscribed 

 swelling about the size of a hulled walnut within twenty- 

 four hours. A somewhat similar method may be used in 

 swine, the injection being made into the ear lobe. An 

 ophthalmic or eye reaction is occasionally used. In this 

 test a tuberculin which has been prepared free from 

 glycerin and other irritant substances must be utilized. It 

 is dropped into the corner of the eye. The eye within 

 twenty-four hours will become inflamed and a marked con- 

 junctivitis will develop. This will disappear within three 

 days. 



The tuberculin test has been proved to be a remarkably 

 reliable method of diagnosing tuberculosis in cattle. It has 

 been used to some extent in diagnosing the disease in other 

 animals as well. The tests used in general resemble those 

 used in cattle. In man, particularly in children, it has been 

 noted that rubbing tuberculin or tuberculin ointment into 

 the skin vigorously will result in the development of a 

 marked reddening at the site of the inunction in tubercu- 

 lous individuals. 



While the tuberculin reaction appears to be a reliable 

 method of recognizing tuberculosis in cattle when carefully 

 carried out, it should be noted that an injection of tubercu- 

 lin may interfere with the thermal reaction of the animal 



