262 MICROBES AND TOXINS 



as to the .probable fate of the patient. The reaction may be 

 negative in exhausted, cachectic tuberculous patients. 



The number of individuals who give a positive reaction 

 much exceeds the number of those who show clinical signs of 

 tubercle : latent dormant tuberculosis, or even healing tubercle, 

 gives a reaction because the body is saturated with the 

 products of its reaction to the tuberculous infection.^ 



In veterinary practice, it happens that animals once sub- 

 jected to tuberculin injection fail to react to a second test 

 performed twenty-five to thirty days after the first ; this fact 

 has been employed in fraudulent dealing to throw out the 

 diagnosis, but the second test will still act if a double dose 

 is given, and if the temperature is taken at the fourth 

 hour (instead of the tenth) ; the fever appears prematurely 

 (Vallee). 



Cutaneous Reactions. — In individuals affected by tuber- 

 culosis, if the skin is subjected to a quite superficial scarifica- 

 tion on which is put a drop of tuberculin, a red spot is seen to 

 appear after a few hours. This swells, and comes to resemble 

 a little vaccine pustule. It was this phenomenon which was 

 discovered by Von Pirquet. Several variations have been 

 tried. It is possible to do without scarification by dropping 

 into the inner corner of the eye a drop of a dilute solution of 

 tuberculin ;' the conjunctiva reacts with more or less intense 

 inflammation and more or less exudate ; this is the ophthalmo- 

 reaction of Wolff-Eisner and of Calmette. 



It was observed during subcutaneous injections of tuberculin, 

 that the needle-track of the syringe, being wetted with a trace 

 of the tuberculin, became red and swelled up ; from this 



1 The statistics of Franz dealing with certain regiments of the Austro- 

 Hungarian army are worth reproducing, since the author had the 

 opportunity of observing the same men during several years. 



In a regiment of four hundred apparently healthy men recruited from a 

 district where tuberculosis was rife, 6 1 per cent, gave during their first year 

 of service a positive reaction ; of 323 similar men in their second year of 

 service 68 per cent, were positive. Of 279 healthy men recruited from a 

 district where tuberculosis was scarce, there were 30 per cent, of positive 

 reaction. These 1002 individuals furnished in the course of the seven 

 following years sixty-four cases of manifest tubercle and twenty died of it. 



