BACILLUS TUBERCULOSIS AND ALLIED ORGANISMS 121 



increasing i decigram of the solution every three days until 

 i c.c. of the pure nitrate can be injected without causing any 

 reaction. A negative reaction sometimes occurs in well- 

 advanced cases, and is, therefore, not a proof of the absence 

 of disease. The reaction is due to the stimulation of irri- 

 tating proteins. Yeast nucleins and other substances have 

 a similar action. This treatment must extend over months. 

 Tuberculin immunity does not last indefinitely. Under this 

 careful treatment, associated with open air, proper food, and 

 general hygiene, Trudeau and his followers have had some 

 very good results. 



Von Pirquet Test. Tuberculin applied to the abraded 

 skin like a vaccination with cow-pox causes a local reaction 

 in tuberculous infants and no reaction in healthy ones. It 

 is not applicable to children over eighteen months of age. 

 The test is so sensitive that it will be positive in the majority 

 of instances, because the majority of people have at some 

 time been affected with tuberculosis or exposed sufficiently 

 to have within them sensitive bodies that are easily stimu- 

 lated. 



Ophthalmic Tuberculin Reaction of Calmette. A modified 

 form of tuberculin is placed on the conjunctiva of an indi- 

 vidual suspected of having tuberculosis. In a few hours a 

 congestion, more or less severe, results, and lasts several 

 days. In healthy persons no reaction occurs. The test is 

 claimed to be harmless, though severe reactions have been 

 reported in tuberculous patients, and even in healthy persons 

 a second application to the same eye may cause an inflam- 

 matory reaction. 



Moro's Test. An ointment of tuberculin and lanolin, equal 

 parts, rubbed in the skin of the arm. A crop of papules de- 

 velops in twelve to twenty-four hours if test is positive. 



Agglutination. Arloing and Courmont have described 

 an agglutination reaction for the tubercle bacillus similar to 

 the Widal reaction of typhoid fever. (See p. 140.) It is 

 very unreliable, however, and but little importance is at- 

 tached to it. 



