600 INFECTION AND IMMUNITY. 



an inflammatory reaction. This is seen most 

 readily in the tubercles of lupus vulgaris, and in 

 the lungs declares itself by an increase in rales 

 and expectoration, caused by the exudation ac- 

 companying the inflammatory reaction. 



For diagnostic purposes the technic of adminis- 

 tration is as follows: It must first be assured 

 that the patient has no continued fever by noting 

 the temperature every two hours for several days. 

 One milligram of tuberculin is injected subcu- 

 taneously, this amount being obtained by suitable 

 dilution of the original solution. It is often advis- 

 able in weak or young subjects to use 0.05 or 0.1 

 mg. Many authorities never exceed 0.1 mg. as an 

 initial dose. If no rise in temperature is produced 

 by this amount,, a second injection of a larger 

 quantity may be given after an interval of two or 

 three days. Koch used as high as 10 mg. before 

 concluding that the reaction is negative. Lowen- 

 stein and others recommend the cumulative action 

 of three or four small doses of tuberculin (0.1 to 

 0.5 mg.) at intervals of three days. The advan- 

 tage of this method is due to the fact that the 

 diagnostic value of a reaction with a small dose 

 of tuberculin exceeds the value of reactions with 

 large doses. By this method, many patients are 

 said to react with the first small dose while the 

 cumulative action of subsequent doses results in 

 a reaction in less susceptible individuals. 

 Theories of Koch explained the tuberculin reaction by the 

 harmful or necrotic effect on the leucocytes and 

 other tissue cells. The substances formed by the 

 breaking down of these cells give rise to the fever 

 and other symptoms. In tuberculous tissues this 

 effect of tuberculin is much more marked. 



