336 IMMUNOLOGICAL METHODS OF DIAGNOSIS 



and in which the results were compared with the clinical findings, 

 it appears that of the clinically tubercular cases 87 per cent, gave 

 the reaction, while this was also found in 20 per cent, of the non- 

 suspected cases. The negatively reacting tubercular cases, v. Pir- 

 quet points out, were almost exclusively cachectic or in the last 

 stages of miliary tuberculosis. 



As the result of a study of 124 children which had come to 

 autopsy and in which the test had been made, v. Pirquet concludes 

 that a positive cutaneous reaction is never observed in the absence 

 of a tubercular lesion; that a negative reaction ordinarily indicates 

 freedom from tuberculosis, but that such a result may also be ob- 

 tained in the last stages of the disease. As a positive reaction ma^ 

 be expected in over 90 per cent, of all individuals after the fourteenth 

 year, it is clear, however, that the diagnostic significance of the 

 reaction is then practically nil. As 35 per cent, of all children, 

 moreover, give a positive cutaneous reaction between the ages of 

 six and ten, it is evident that even at this age its diagnostic value 

 is limited. 



The Tuberculin Test According to Calmette (Conjunctival Method). 

 While Calmette advocates the use of a tuberculin which essentially 

 contains the alcohol-insoluble constituents of bovine tubercle bacilli, 

 made up into a | per cent, aqueous solution, one may also employ 

 a 5 per cent, solution of the old tuberculin of Koch. One or two 

 drops of either solution are placed upon the conjunctiva of one eye 

 near its inner canthus, when the lids are held together for about 

 a minute. In the normal individual slight redness may then develop 

 and persist for a few hours, after which it disappears. In the tuber- 

 cular subject, on the other hand, marked hyperemia occurs after 

 three to six hours (more rarely after twelve to twenty-four hours); 

 this principally affects the lower lid, the lower portion of the eye- 

 ball, the caruncle, and the semilunar fold (see Plate IX). At the 

 same time there is some swelling and secretion, which in severe 

 reactions becomes mucopurulent. 



The height of the reaction is reached after ten to twelve hours, 

 after which the inflammatory manifestations usually disappear and 

 there is a return to the normal. 



While in most cases no unduly severe reactions occur, such have 

 nevertheless been noted in isolated cases, and a number of observers 

 look upon the method in its original form as dangerous and not 



