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persons. It consists of a sterilized alcoholic or glycerine extract of 

 the material upon which the bacillus tuberculosis has been grown. 

 What the active principle of the lymph is has not been determined, 

 but is supposed to be a complex chemical compound generated by 

 the growing germs. 



While it was found not to cure consumption when injected in 

 small quantities into the circulation, its injection into the body of 

 a consumptive person was followed by the appearance of febrile 

 symptoms : rise of temperature, increased action of the heart, 

 slight headache, chills, etc. These phenomena did not appear 

 when the lymph was injected under the skin of one not suffering 

 from the disease. 



This forms the basis for the employment of the lymph in the 

 diagnosis of tuberculosis in domestic animals. As a result of nu- 

 merous and careful experiments it has been found very reliable, in 

 fact, almost infallible. The condition of the internal temperature, 

 for twenty-four or more hours after its injection, as determined by 

 the use of a thermometer, shows the existence or non-existence of 

 tuberculosis. 



A rise of the internal temperature several degrees above the 

 normal within twenty-four hours after the injection would, in the 

 absence of other conditions which might cause the same change, 

 indicate the existence of tuberculosis. A stationary or normal 

 temperature indicates the non-existence of the disease. 



For the reason that disease or other conditions may alter or 

 raise the temperature at any time, it is necessary that tuberculin 

 be used by one well acquainted with ordinary diseases and their 

 symptoms, so as to be able to determine whether the elevation fol- 

 lowing the injection of tuberculin comes as the result of the use of 

 the lymph or is an accompaniment to some developing disease. 



In all cases of "reaction "it becomes necessary to prove that 

 the rise of temperature has not been caused by some inflammatory 

 trouble independent of tuberculosis before we can say that the 

 " reaction " indicates the existence of tuberculosis. 



Properly used by a competent veterinarian tuberculin is practi- 

 cally infallible in the diagnosis of tuberculosis. By its use alone 

 can we with any degree of accuracy be reasonably sure of our 

 opinion as to whether tuberculosis does or does not exist in an an- 

 imal ; and so extremely delicate is the test that its use is followed 

 by a marked reaction though there be but one or two tubercles 

 present in the body. 



We frequently hear this question : " If I test my cows with tu- 

 berculin may I not introduce the disease into the herd or produce 

 the disease in the healthy animals ? " We answer. No. Tuber- 



