606 INFECTION AND IMMUNITY. 



or minimum local reaction occurs. Larger amounts 

 which would cause febrile reactions and eventually 

 render the patient resistant to tuberculin and thus 

 preclude the local changes are to be avoided. It is 

 customary to begin with 0.1 to 0.05 milligrams 

 and gradually to increase the amount injected. 

 If fever is caused by a particular dose, larger 

 amounts are not to be given until fever ceases to 

 follow this dose. By the time a dosage of 50 milli- 

 grams is reached, which may require many months, 

 the patient usually has lost the power of reacting 

 and the injections are to be interrupted until Le 

 again becomes sensitive to the toxin (from three 

 to six months), after which treatment should be 

 resumed. Cure is recognized when the patient hc.s 

 lost permanently the power to react, his condition 

 then being identical with that of the healthy man. 



The principles on which the action of tuberculin 

 depend are hypothetical. Marmorek says that the 

 fever and local changes are due to a special toxin 

 (the true toxin), which the bacillus secretes under 

 the stimulation of the tuberculin. Ehrlich sup- 

 poses that cells adjacent to the tubercles have been 

 injured moderately by the tuberculin which is pro- 

 duced in situ, and that as a consequence of this 

 injury such cells are particularly susceptible to the 

 additional tuberculin which is injected, and react 

 to the stimulus by proliferation (Marx). In ac- 

 cordance with this conception the fever also in 

 some obscure way is related to the local reaction. 



It is probable that the therapeutic value of 

 tuberculin depends on the utilization of the sub- 

 cutaneous and other body cells as a source of anti- 

 bodies. The formation of these antibodies follows 

 the injection of tuberculin, whereas in the tuber- 



