TUBERCULIN REACTION 637 



in from twenty-four to forty-eight hours, and usually disappears in 

 from six to ten days. The salt solution generally produces a trau- 

 matic reaction, similar to a mild tuberculin reaction, which subsides 

 in forty-eight hours. 



The reactions are best recorded after twenty-four hours, and the 

 simplest method of recording the results is to measure the width of the 

 area of infiltration of each reacting point. 



THE CUTANEOUS TUBERCULIN REACTION (VON PIRQUET) 

 Variety of Tuberculin. Undiluted old tuberculin is now used almost 

 exclusively in conducting the test. 



Method of Conducting the Test. 1. The flexor surface of the fore- 

 arm is chiefly used for making the applications, but it should be re- 

 membered that tests performed on different portions of the body are 

 not strictly comparable. 



2. The skin is cleansed lightly with alcohol and dried. Three abra- 

 sions are made, about lJ/ or 2 inches apart, with a von Pirquet skin 

 borer (Fig. 126) or with a needle, small lancet, or blood sticker. The 

 object is to scarify the superficial layers of the skin, avoiding as much as 

 possible bleeding, although a few small points of blood should appear. 

 To the upper and lower abrasions add a drop of tuberculin; after ten 

 minutes wipe away the excess with a bit of cotton. No shield or pro- 

 tective dressings are required. The middle abrasion is the control, 

 and shows the amount of traumatic reaction following the scarifying 

 process. Due precautions should, of course, be observed that none of 

 the tuberculin flows down the arm and reaches this spot. 



3. The tests are inspected at the end of twenty-four hours. 



The Reaction. The traumatic reaction as shown in the control 

 area may present an inflammatory areola with, at times, slight infiltra- 

 tion. Before a test may be considered positive its areola should be at 

 least five millimeters wider than the control area. The reactions are 

 usually designated as follows: 



1. Negative Reaction. No appreciable difference between the tu- 

 berculin areas and the control. 



2. Slight Reaction. Definite but slight redness with some infiltration. 



3. + Reaction. A wider area of redness, with definitely raised 

 centers. 



4. ++ Reaction. Wider area of redness, with more marked in- 

 filtration than +. 



5. + + + Reaction. Unusual redness and a wide area of infiltra- 

 tion, all cases which go on to vesiculation. 



