320 PATHOGENIC BACTERIA. 



of a cubic centimeter an inflammatory and febrile reac- 

 tion occurs. The inflammation sometimes causes super- 

 ficial tuberculous lesions (lupus) to ulcerate and slough 

 away, and for this reason is of some value in therapeutics, 

 although attended with the dangers mentioned above. 

 The fever is sufficiently characteristic to be of diagnostic 

 value, though the tuberculin can only be used as a diag- 

 nostic agent in practice upon animals. 



The tuberculin test of cows and other animals suspected 

 of having tuberculosis is easily carried out. The tuber- 

 culin as Koch prepared it is now known as "concentrated " 

 or " Koch's tuberculin," to differentiate it from the "di- 

 luted tuberculin," which is the same thing so diluted 

 with i per cent, carbolic acid solution that i cubic centi- 

 meter equals a dose. The dose of the concentrated tuber- 

 culin is 0.4-0. 5 c. cm., that of the diluted tuberculin ic.cm. 



For the test to be a satisfactory diagnostic one, the 

 temperature of the animal should be taken every few 

 hours for a day or two before the tuberculin is to be used, 

 in order that the normal diurnal and nocturnal variations 

 of temperature shall be known. The tuberculin is then 

 administered by hypodermic injection into the shoulder 

 or flank, and the temperature taken every two hours for 

 the next twenty-four hours. A reaction of two degrees 

 beyond that normal to the individual animal is positive 

 of tuberculosis. After one reaction of this kind the ani- 

 mal will not again react to a like dose of tuberculin for 

 weeks or months. 



It is not impossible that the serum-agglutination test 

 may, in the future, be applied to the diagnosis of tuber- 

 culosis. Arloing found that when to homogeneous cult- 

 ures of the tubercle bacillus the serum of a normal goat 

 is added, no change occurs. If, however, the serum is 

 from a goat that has received injections of strong tuber- 

 culin or of tubercle bacilli, typical agglutinations like 

 those of Widal's typhoid test occur. 



The action of tuberculin upon the animal organism is 

 peculiar, but readily understandable. // does not exert 



