I024 



TUBERCULIN AND THE TUBERCULIN REACTION 



cytes is observed, but within a few hours there is a complete restoration to normal 

 from this very slight change. 



When a similar injection is made into the skin of a tuberculous animal, again no 

 immediate effect is apparent, but within eight to twenty-four hours an acute local in- 

 flammation takes place at the site of injection. A red, raised area, with central blanch- 

 ing, 1-2 cm. in diameter, appears, which is of firmer consistency than the surrounding 

 skin. If the animal is exceptionally sensitive, or the tuberculin solution concentrated 





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Fig. 4. — Tubercle in lung of guinea pig net treated with tuberculin. Note sharp border and 

 normality of lung parenchyma around tubercle. 



in active principle, central necrosis occurs. Microscopically, the capillaries are seen 

 to be dilated and engorged, and an intense infiltration of large mononuclear and small 

 polynuclear leukocytes is observed. There is an increase in the intercellidar fluid, 

 and some coagulated fibrin may be present. When the reaction is carried out in a 

 parenchymatous organ with more specialized cells than those present in the skin, such 

 as the testis, necrosis of the parenchymatous cells is a regular accompaniment of the 

 reaction. Petersen and Levinson^ have demonstrated an increase in capillary per- 

 meability in sensitized tissues, which appears to be fundamental to the reaction. 



This is obviously an acute inflammation with all of the rubor and tumor and not 

 without the calor and dolor demanded by the ancient definition. The mechanism in- 



' Petersen, W. F., and Levinson, S. A.: Am. Rev, Ttderc, 8, 122. 1923. 



