146 SPECIAL BACTERIOLOGY 



results since confirmed by other investigators. In preparing the original 

 tuberculin, according to Kiihne's investigations, the ordinarily prepared 

 culture media contain so much peptone that there is always more or 

 less albumose present, rendering it impossible to separate the true 

 products of the bacillus from other substances present in the culture 

 media, hence special culture media formulae are used by some investi- 

 gators. Koch in his original method, after testing the purity of six to 

 eight weeks' old veal bouillon cultures of the tubercle bacilli by 

 microscopical examination, poured them into a suitable vessel, and 

 evaporated to one-tenth the original volume over a water-bath. The 

 liquid was then filtered through porcelain. The crude tuberculin 

 obtained by this process contains 40 to 50 per cent, of glycerine, is 

 soluble in water, insoluble in alcohol, passes readily through dialyzing 

 membranes, and is not destroyed by a boiling temperature, keeps well, 

 and preserves its activity indefinitely. 



The original tuberculin is very valuable as a diagnostic agent in bovine 

 tuberculosis. For this purpose it is diluted with 9 parts of water con- 

 taining J per cent, of carbolic acid. About 3 c.c., or 60 minims, are 

 injected subcutaneously ; the point of injection is immaterial, but the 

 side of the neck where the skin is thin is the most suitable place. It is 

 also more practical to use a large-sized inoculating needle instead of the 

 smaller varieties ; the hair is clipped from the part selected, which is 

 thoroughly cleansed and disinfected before the injection is made. Before 

 the tuberculin test is applied, the temperature of the animals ought to 

 be taken every two hours, at least six or seven times before the 

 injections are made, as in many animals the variations are sufficiently 

 constant to make their determination by precise measurements practi- 

 cally necessary in every tuberculin test from which reliable results are 

 expected. After the injection is made the temperature ought to be 

 taken again in eight to ten hours, and from then on every two hours, 

 until a decided reaction, continuous during several hours, has occurred, 

 or until eighteen to twenty hours have elapsed since the time of injection. 

 The febrile reaction in tuberculous cattle, following the subcutaneous 

 injection of tuberculin, begins six to ten hours after the injection, reaches 

 the maximum in nine to fifteen hours, and returns to the normal in 

 eighteen to twenty-six hours after the injection. The elevation in the 

 temperature sufficient to constitute a reaction has variously been given 

 from 0*5 to 1 C., but consideration of the number of degrees the 

 temperature after the injection rises above the temperature before the 

 injection is not alone sufficient the height of the temperature and the 

 duration of the reaction must also be taken into account ; advanced cases 

 of tuberculosis occasionally fail to react, while the reaction is frequently 

 highest in young animals in the first stage of the disease. In fact, the 

 variation of the temperature of an animal during the course of the day is 

 frequently so great that if the variation is not determined, and the 



