SPECIFIC BACTERIAL REACTIONS 181 



fected individual. The reaction is very delicate, thus 

 accounting for the high percentage of positive results. 

 The test has its greatest applicability in children and 

 patients exhibiting a comparatively high fluctuating 

 temperature. Old tuberculin (" O. T."), again, is 

 the preferable preparation in the performance of von 

 Pirquet's test. It is conveniently put up in sealed 

 capillary tubes and marketed by a number of pharma- 

 ceutical firms. The technic is quite similar to vac- 

 cination against smallpox. An area on either the arm 

 or leg, usually the forearm, is cleansed with ether, not 

 alcohol or soap and water, and a drop of " O. T." 

 is placed on the skin ; about two inches distant a second 

 drop of glycerin bouillon, utilized as a control, is 

 placed. With a lance, a needle or special scarifier, im- 

 mersed first in the central drop, then the drop of tuber- 

 culin, the epidermis is lightly scratched, removing 

 only the superficial epithelium and avoiding, if pos- 

 sible, any evidence of blood. The drops should be al- 

 lowed to evaporate to dryness, before applying a dress- 

 ing of sterile gauze, otherwise they may be covered 

 with a vaccine shield. At most a very slight hyper- 

 emia, disappearing in twenty-four to forty-eight 

 hours, due to traumatism, may be noted at the control 

 point. A typical positive reaction at the site of the 

 tuberculin drop is characterized by a hypersemic and 

 inflammatory area from four millimetres to three 



