TUBERCULOSIS— CONSUMPTION 403 



Other aids to diagnosis must be employed, the principal ones 

 of which are the following: 



1. The Tuberculin Reaction. — Tuberculin may be applied 



in several different ways. The most important methods of 



application given in the order of practical importance are 



, the following: (a) The subcutaneous; (6) . conjunctival, and 



(c) dermal. 



(a) The subcutaneous application of tuberculin, which 

 consists in injecting the tuberculin in proper dosage into the 

 loose connective tissue under the skin, is as yet the best 

 known and most reliable method. The reaction following is 

 general in that it induces in tuberculous animals (best in 

 cattle) a febrile temperature which usually begins in six 

 to eight hours, reaches its acme in twelve to twenty hours, 

 and lasts for twenty-four to forty hours after the injection. 

 (For detail of technic, • interpretation, etc., see Malkmus' 

 Clinical Diagnostics.) Tuberculin properly used is a very 

 reliable diagnostic agent. In 98 per cent, of the cases a 

 positive reaction indicates the presence of a tubercular 

 lesion which can be determined on necropsy. Tuberculous 

 animals may not react to the test under the following 

 conditions: 



(1) When the disease is in the period of incubation 

 (Moore). 



(2) When the progress of the disease is arrested. 



(3) In advanced, generalized cases and the condition of 

 the patient is bad. 



(4) When the animal has been just previously (within four 

 weeks) injected with tuberculin. 



In the last two instances cited (3 and 4), by increasing 

 the dose of tuberculin, a reaction is apt to follow. 



(b) The conjunctival application consists in instilling into 

 the conjunctival sac a few drops of tuberculin (undiluted). 

 In tuberculous cattle in six to twenty-four hours symptoms of 

 conjunctivitis develop (congestion, swelling, lacrimosis) with 

 the accumulation of a yellow, flocculent exudate in the inner 

 canthus of the eye. The reaction may last two to four days. 

 It is spoken of as positive when the conjunctivitis is pro- 

 nounced and the exudate purulent. Milder reaction (simple 



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