INFECTIOUS DISEASES OF CATTLE. 409 



The tuberculin test came into existence through the most careful 

 and thorough scientific experimentation. In practice it is applied by 

 first taking the temperature of the animal to be tested, at intervals 

 of about two hours, a sufficient number of times to establish the nor- 

 mal temperature of the body under the ordinary conditions of life. 

 The proper dose of tuberculin is then injected under the skin with a 

 hypodermic syringe between 8 and 10 p. m. on the day of taking the 

 preliminary temperatures. On the following day the temperatures 

 are taken every two hours, beginning at 6 a. m. and continuing until 

 twenty hours following the injection, if the fullest information is 

 desired." From average temperatures calculated by De Schweinitz 

 in 1896 of about 1,600 tests of tuberculous cows, it appears that in 

 general the rise of temperature begins from five and one-half to six 

 hours after the tuberculin is injected, reaches its greatest height from 

 the sixteenth to the twentieth hours, and then gradually declines, 

 reaching the normal again by the twenty-eighth hour. 



As a result of this method an accurate diagnosis may be established 

 in over 97 per cent of the cases tested. The relatively few failures 

 in diagnoses are included among two classes of cattle. The first class 

 contains those that are tuberculous, but which do not react either be- 

 cause of the slight effect of an ordinary-sized dose of tuberculin on 

 an advanced case of the disease with so much natural tuberculin 

 already in the system, ot on account of a recent previous test with 

 tuberculin which produces a tolerance to this material lasting for 

 about six weeks. The second class includes those that are not tuber- 

 culous, but which show an elevation of temperature as a result of 

 (a) advanced pregnancy, (b) the excitement of oestrum, (c) concur- 

 rent diseases, as inflammation of the lungs, intestines, uterus, udder, 

 or other parts, abortion, retention of afterbirth, indigestion, etc., 

 (d) inclosure in a hot, stuffy stable, especially in summer, or exposure 

 to cold drafts or rains, (e) any change in the method of feeding, water- 

 ing, or stabling of the animal during the test. Notwithstanding all 

 these possibilities of error, the results of thousands of tests show that 

 in less than 3 per cent of the cases tested do these failures actually 

 occur. In the first class the chances of error are decidedly reduced by 

 the skilled veterinarian by making careful physical examination and 

 diagnosing clinically these advanced cases, and by the injection of 

 double or triple doses into all recently tested cattle, with the taking 

 of the after temperatures, beginning two hours following the injection 

 and continuing hourly for twenty hours. 



o The oculo-tuberculin test and the cuto-tuberculin test, as their names imply, 

 consist in the application of the tuberculin to the eye and to the scarified skin of 

 the animal to be tested. These methods will not be discussed at present, as they 

 are still in the experimental stage. 



