286 AGRICULTURAL BACTERIOLOGY 



sary to take temperatures until eight to ten hours after the 

 injection of the tuberculin. On account of the length of 

 this period, it is most convenient to inject the tuberculin in 

 the evening. Four or five temperature readings should be 

 taken at two-hour intervals until there is a marked and 

 permanent decline toward the normal. In the case of a 

 positive reaction, the temperature usually begins to rise 

 from 10 to 14 hours after injection, reaches a maximum 

 in from 12 to 16 hours, and then declines rapidly. The 

 maximum temperature may reach from 105 to 107 F., or 

 three to five degrees above the average normal temperature. 

 The reaction is considered positive when the highest tem- 

 perature after the injection is at least two degrees above the 

 average normal before injection, or is one and five tenths 

 degrees above the highest temperature noted before injec- 

 tion. 



It is often a question of judgment as to whether a re- 

 action is positive or not, especially in those cases in which 

 the increase just reaches the standards assumed. In those 

 cases, all circumstantial features, including especially the 

 character of the temperature curve, must be taken into con- 

 sideration. In no case should the decision of such doubtful 

 cases be left in the hands of persons who are not thoroughly 

 familiar with such work. The limitations of the test must 

 be recognized, and the results must always be interpreted 

 with judgment. 



In making the test, conditions should be kept as nearly 

 normal as possible. The herd should be kept quiet, fed, and 

 watered as usual, unless the manner of watering would per- 

 mit them to drink large quantities of cold water, which 

 might vitiate the results by excessive reduction of tempera- 

 ture. Preferably water should be given in small quanti- 

 ties, if it is cold. 



Animals that show a doubtful reaction should be retested 



