PHENOMENA OP SUPERSENSITIVENESS 291 



heading of Anaphylaxis, anrl it may be said that anaphylaxis 

 is observed when living or dead tubercle bacilli are injected 

 into healthy animals. The'tuberculin reaction is much used in 

 diagnosis and, in addition to the methods just described, the 

 following special modifications are frequently used for this 

 purpose : — 



(b) The Cutaneous Tuberculin Reaction of von Pirquet and 

 the Ophthalmo-reactionof Calmette. — In recent times the diagnosis 

 of tuberculosis has been considerably aided by the introduction 

 of these two tests. Both are essentially of the same nature, and 

 depend, like the original tuberculin reaction, on the sensitiveness 

 of the tissues of tubercular patients to tuberculin. 



The cutaneous test is carried out as follows : The skin, usually 

 that of the flexor aspect of the forearm, is well cleansed with 

 ether and then allowed to dry. Two drops of tuberculin are 

 placed on the prepared surface about four inches apart, and then 

 midway between the two drops a small spot is scarified with a 

 small metal bore constructed for the purpose. This serves as a 

 control, any reaction which follows in it being merely a traumatic 

 one. Similar scarification is effected through the drops of 

 tuberculin, so that the scarified spots are exposed to its action. 

 Small portions of cotton wool are placed over the drops to pre- 

 vent the tuberculin from running off, and the latter is allowed to 

 act for ten minutes. After that time the cotton wool is removed ; 

 no dressing is required. In the process of scarification only the 

 epidermis should be injured and blood should not be drawn. 

 The " old " tuberculin of Koch is that used. In the case of a 

 positive reaction an inflammatory redness and swelling make 

 their appearance round the sites of tuberculin inoculation, 

 generally within a few hours, and at the end of twenty-four 

 hours there is a distinct inflammatory papule about half an inch 

 in diameter, with a somewhat paler centre like a spot of urticaria ; 

 sometimes in the centre there are minute vesicles. The maximum 

 effect usually occurs within forty-eight hours, and after that time 

 the reaction gradually recedes. Such is the typical reaction, but 

 of course slighter, and also more intense reactions are met with. 

 In a negative reaction all three points of scarification show 

 merely a slight traumatic redness which soon passes off. 



For the ophthalmoreaction Calmette uses a purified tuberculin. 

 The tuberculin is prepared as in Koch's original method, and is 

 precipitated with 95 per cent, alcohol ; the precipitate is then 

 dissolved in water. This process is repeated other two times, 

 and the final precipitate is made up as a 1 per cent, solution in 

 distilled water. For use, in the case of an adult, a drop of this 



