578 Tuberculosis. 



be regarded as tuberculous while all post-injection temperatures above 

 103.1 but not exceeding 104 must be regarded as doubtful and be con- 

 sidered individually. 



In interpreting tlie results of a tuberculin test the highest 

 temperature recorded after the injection of the tuberculin is 

 of paramount importance because the existence of a reaction 

 is based upon the presence of a distinctly febrile condition. The 

 difference between the highest pre-injection and the highest 

 post-injection temperatures is next in importance though of 

 less value. The highest pre-injection temperature must of 

 course always constitute the basis of our considerations. 



Tuberculin reactions will occur in very early stages of 

 tuberculosis. Nocard and Rossignol observed reactions from 

 the 32nd to the 48th day after alimentary infection, from the 

 19th to the 32nd day after inhalation infection and on the 13th 

 day after injection of the virus into the udder, while experi- 

 ments made by the Royal Agricultural Society showed that 

 reactions occurred on the 8th day after the subcutaneous in- 

 jection or the alimentary administration of infectious material. 

 According to MacFadyean the maximum time elapsing between 

 infection and reaction to tuberculin is 51 days. 



In some cases repeated injections of tuberculin result in 

 immunity to its action. Thus some cattle that are injected 

 subcutaneously with the usual dose, will fail to react, or will 

 react only slightly to a second application of tuberculin. 

 Accordingly it is only possible to judge the results of a tuber- 

 culin test correctly when it is positively known that the animal 

 in question was not treated with tuberculin at any time during 

 the preceding four weeks. 



Nocard 's pertinent experiments showed that of 24 reacting cows 

 only 33% reacted to a test applied 24 to 48 hours later, 50% reacted 

 after one week, 60% after two weeks and nearly all of them reacted 

 after the lapse of one month. According to results obtained at the 

 Prussia sea-quarantine stations, however, cattle previously treated with 

 tuberculin will always react if five times the ordinary dose is adminis- 

 tered, and Vallee's experiments have shown that cattle will react to 

 double doses administered 36 to 48 hours after a previous injection 

 of tuberculin. In such cases, however, the reactions set in earlier (4th 

 to 9th hour) and are of shorter duration, hence the necessity of record- 

 ing post-injection temperatures at two-hourly intervals beginning im- 

 mediately after the injection of the tuberculin. 



Malm, Lignieres, Mettaru and Liieders report similar experiences. In experi- 

 ments made by Klimmer and Kiesig 88.3% of cows receiving an ordinary dose 

 of tuberculin reacted to a double dose administered aft^r one to three weeks. 

 The second reaction usually began at or after the 7th hour, but earlier in 18.5% 

 of the eases and usually lasted only two hours, occasionally only one hour and the 

 maximum temperatures were lower than in the first reactions. On the other hand, 

 Zabala observed that injections of the usual dose, repeated several times at two 

 days ' intervals would prevent reactions to subsequent excessive doses. According 



