Toxic Products 335 



reaction caused by the injection of tuberculin into tubercu- 

 lous animals is an important adjunct to our means of diag- 

 nosticating the disease. For the recognition of tuberculosis 

 in cattle it is easily carried out. 



To make a satisfactory diagnostic test the temperature of 

 the animal should be taken every few hours for a day or two 

 before the tuberculin is administered, in order that the nor- 

 mal diurnal and nocturnal variations of temperature shall 

 be known. The tuberculin is then administered by hypoder- 

 mic injection into the shoulder or flank, and the tem- 

 perature subsequently 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 animal will not again 

 react to an equal dose of tuberculin for a number of weeks. 



Tuberculin does not exert the slightest influence upon the 

 tubercle bacillus, but acts upon the tuberculous tissue, aug- 

 menting the poisonous influence upon the cells surrounding 

 the bacilli, destroying their vitality, and removing the condi- 

 tions favorable to bacillary growth, which for a time is 

 checked. This action is accompanied by marked hypere- 

 mia of the perituberculous tissue, with transudation of 

 serum, softening of the tuberculous mass, and its absorp- 

 tion into the blood, a marked febrile reaction resulting 

 from the intoxication. 



Virchow, who well understood the action of the tuberculin, 

 soon showed that as a diagnostic and therapeutic agent in 

 man its use was attended by grave dangers. The destroyed 

 tissue was absorbed, but with it some of the bacilli, which, 

 being transported to new tissue areas, could occasion a 

 widespread metastatic invasion of the disease. Old tuber- 

 culous lesions which had been encapsulated were sometimes 

 softened and broken down, and became renewed sources of 

 infection to the individual, so that, a short time after an 

 enthusiastic reception tuberculin was placed upon its proper 

 footing as an agent valuable for diagnosis in veterinary 

 practice, but dangerous in human medicine, except in cases 

 of lupus and other external forms of tuberculosis where the 

 destroyed tissue could be readily discharged from the surface 

 of the body. 



Many, however, continued to use it, and Petruschky* has 

 *" Berliner klin. Wochenschrift," 1899, Dec. 18-25. 



