76 IMMUNITY 



The Tuberculins. 



The toxin of the tubercle bacilli -(old tuberculin) is prepared by 

 growing the organism for a long period in glycerinized veal broth, 

 after which the flasks are steamed in a sterilizer for an hour or more, 

 and then the bacilli are filtered out through porcelain filters. The 

 filtrate is reduced by boiling to -^ of its bulk, and to this a half of one 

 percent of carbolic acid is added as a preservative. If this toxin, 

 even in minute doses, is injected under the skin of a tuberculous 

 animal, it acts as a powerful poison. In a few hours, it causes a 

 rapid rise of body temperature, accompanied by nausea and, per- 

 haps, vomiting. About the localized foci of tuberculosis, a vigorous 

 reaction occurs. Around indolent old sores and other lesions there 

 is a tendency to heal by the casting off of necrosed tissues, and the 

 infiltration of the peritubercular area with leucocytes. In lupus 

 (tuberculosis of the skin) redness and heat occur about the lesion. 

 This febrile phenomenon following the injection of tuberculin into 

 tuberculous animals is a valuable diagnostic feature toward the 

 recognition of tuberculosis in animals and in man. In 90 percent 

 of cases the reaction is trustworthy. 



Tuberculin acts as a fever producer in an unknown way. It is 

 supposed, however, that the intense local reaction produces fever 

 through active tissue changes. 



Its use in man has been much questioned, as it is thought by some 

 to disseminate the disease from original and confined foci. This 

 however has been denied. Many able clinicians use it and recom- 

 mend it. (Osier, Trudeau, Musser.) 



Koch's new, or T.R. tuberculin was, like the old, designed by him 

 as a therapeutic agent for the cure of tuberculosis. It is made by 

 pulverizing the bodies of living tubercle bacilli and dissolving the 

 residuum in an indifferent fluid, centrifuging this and collecting 

 the sediment which is Tuberculin Rest, T.R. The solution above 

 this sediment containing soluble substances from the bacillary 

 bodies is Tuberculin Obers, T.O. It produces a more intense 



