304 AGEICULTUEAL AND INDUSTRIAL BACTERIOLOGY 



the products of growth of the tubercle bacillus. Conse- 

 quently it is possible by growing the tubercle bacilli in the 

 laboratory in broth, killing the organisms by heat, filtering 

 and concentrating the product to develop what is practically 

 a glycerin extract of tubercle bacilli which, when injected 

 into animals suspected of having tuberculosis, will deter- 

 mine the presence or absence of the disease by the reaction 

 produced. If the injection is made subcutaneously, there 

 will generally develop in from twelve to sixteen hours after 

 injection a fever leading to a rise of one or more degrees in 

 the temperature. If the injection is made into the skin 

 there may be considerable local swelling developed. A 

 purified tuberculin brought into contact with the mucous 

 membrane covering the eye will cause decided inflammation. 

 The material thus prepared for diagnosing tuberculosis has 

 been termed tuberculin. A similar material prepared from 

 glanders bacilli termed mallein has been extensively used in 

 the diagnosis of glanders in the horse. 



