PIRQUET REACTION. 603 



reached by Trudeau, Baldwin and Kinghorn in 

 animal experiments in which, "as in previous ob- 

 servations, a favorable absorptive influence was 

 noted on the diseased focus." Bearing in mind 

 the limitations mentioned above, and the possibil- 

 itj of the reaction being induced by leprosy, acti- 

 nomycosis and syphilis ( ?), the statement of Osier 

 may be quoted that "in obscure internal lesions, 

 in joint cases and in suspected tuberculosis of the 

 kidneys the use of tuberculin gives most valuable 

 information." 



Yon Pirquet made use of the increased capa- 

 bility of the skin of tuberculous patients to react v 

 to tuberculin as a means of diagnosis of tuber- 

 culosis (see Anaphylaxis). The test is carried out 

 as follows: The ventral surface of the forearm is 

 cleansed with ether and two drops of old tuber- 

 culin are placed on the skin at points about 10 cm. 

 apart. The skin underneath the tuberculin is 

 then scarified over an area about the size of a pin- 

 head, as for an ordinary small-pox vaccination. A 

 small quantity of cotton is then placed over the 

 scarifications until they are dry. A third scarifi- 

 cation is made about 10 cm. from one of the first 

 two and no tuberculin iised. This is to be used 

 as a control. 



The ensuing reactions are described by v. Pir- 

 quet as follows : 



1. Traumatic reaction: The vaccination and 

 control sites show in a few minutes a small papule 

 surrounded by a soft red areola which disappears 

 in a few hours. There remains a small slightly 

 raised pinhead-sized red spot which becomes cov- 

 ered with a crust. This is succeeded by pigmenta- 



