496 IOWA DEPARTMENT OF AGRICULTURE 



The diagnosis of tuberculosis in cattle presents no alternative 

 save the use of tuberculin, it being recognized by the leading au- 

 thorities of this and foreign countries that the positive diagnosis 

 of tuberculosis in most living animals is impossible without the 

 use of tuberculin. 



Tuberculin is the boullion in which the tubercle bacillus has been 

 grown, charged with the toxic products of its growth, but which has 

 been raised to boiling temperature to destroy all germ life, and 

 from which the dead germs have been removed by passing through 

 a porcelain filter. When a physiological dose of this has been in- 

 jected, subcutum, into the suspected animal, it has no effect upon 

 the non-tuberculous, while in the tuberculous it produces, in the 

 course of the next twenty- four hours (usually from the eighth 

 to the sixteenth), a steady rise of temperature by 2 degrees F. or 

 more, followed by a slow subsidence to the normal. This may last 

 for from three to ten hours in different cases. 



The following precautions should be observed: 



1. The temperature of the animal is best taken at intervals, or at 

 least morning, noon and night, on the day of injection to show that the 

 animal has no habitual rise at any time of the day. 



2. The subject must be in good general health. If there is present 

 in the system any concurrent disease it may undergo an aggravation 

 within twenty-four hours and give a rise of temperature that will be 

 mistakenly set down for tuberculosis. At the very start, therefore, it is 

 important that the general health of the animal should be first assured 

 by a critical professional examination. If some other disease is present 

 the Tuberculin test had best, as a rule, be delayed until that has sub- 

 sided, while if tuberculosis be found the test will be superfluous. 



3. The cows should not be tested while in advanced pregnancy or 

 about to abort. In many cases, though not in all, as preparations are 

 made for calving, the system becomes unduly susceptible to the pres- 

 ence of tuberculin and that agent will cause a rise of temperature, al- 

 though no tuberculosis is present. Unless this source of error is care- 

 fully guarded against, the most valuable cows in the herd may be con- 

 demned unjustly. 



4. The cow must not be within three days of the period at which 

 "heat" would naturally occur. Under the excitement of oestrum the 

 body temperature usually rises from two to three degress, and if tuber- 

 culin has been used this rise may be attributed to tuberculosis and a 

 sound animal may be condemned. Abortions sometimes take place un- 

 expectedly and unknown to the owner. If, therefore, a cow under the 

 test, and which is not advanced in pregnancy, should show a rise of 

 temperature, it should at once be ascertained whether or not the ani- 

 mal is in "heat." If symptoms of "heat" are found she should be set 

 aside along with any calving cows to be tested again when such source 

 of error is no longer present. 



