DIAGNOSIS. 599 



taneously without abscess formation and is ab- 

 sorbed with some rapidity. An animal or person 

 immunized with TE is immune to all the constitu- 

 ents of the bacillus. The condition produced by 

 active immunization is one of increased resistance 

 rather than of absolute immunity; large doses of 

 bacilli may cause infection. The nature of the 

 new resistance is not satisfactorily established. 

 Inasmuch as tuberculin is used not only for 



,. -IIP , . in Diagnosis. 



diagnosis but also for curative purposes in man 

 (active immunization), and since the principles of 

 action are similar in both instances, the use of 

 tuberculin may be considered at this point. A 

 healthy man is not susceptible to moderate doses, 

 but a tuberculous man is even more susceptible 

 to the toxin than the tuberculous guinea-pig, 

 since 1 mg. often causes an intense reaction. 

 Weigert classifies the disturbance which tuber- 

 culin may produce in the tuberculous as thermal, 

 circulatory, respiratory, digestive, nervous and 

 vasomotor, and secretory. Necrosis may be pro- 

 duced at the point of injection. In so far as the di- 

 agnostic use of tuberculin is concerned, we are in- 

 terested chiefly in the thermal disturbances, 

 which are accompanied by chills, malaise and 

 muscular pains. Following injection of a suitable 

 quantity, a period of incubation of from eight to 

 fourteen hours follows, and at the end of this time 

 the temperature rises progressively for two or 

 more hours and may reach a maximum of from 40 

 to 41 C. ; after remaining at this point for from 

 two to six hours, it recedes rapidly. In addition 

 to this general reaction, the toxin causes conges- 

 tion, redness and swelling at the site of the tuber- 

 culous lesions, i. e., the foci become surrounded by 



