THE PHENOMENA OF INFECTION 465 



tization, or the tuberculous reaction, in contradistinction 

 to the second, or the reaction of local sensitization. 



When a solution of tuberculin is applied to the conjunc- 

 tival sac of a tuberculous individual, no changes are usually 

 noticed for an interval varying from six to forty-eight 

 hours. At the end of this time there is a slight smarting 

 or gritty sensation complained of, the patient often referring 

 to it as a sensation of sand in the eye. The examination of 

 the conjunctiva at this time reveals a reddening and swelling 

 of the mucous membrane of the lower lid and the caruncle. 

 This inflammatory reaction gradually increases in intensity 

 until from ten to fifteen hours have elapsed, at which time 

 it has usually reached a maximum, and after which a gradual 

 recession occurs, until at the end of from two to four days, 

 occasionally after a longer interval, the conjunctiva has 

 again regained its normal appearance. At the height of 

 the reaction, and on awakening in the morning, it is not 

 uncommon to observe a slight fibrinous or fibrinopurulent 

 exudate accompanying the inflammatory reaction. 



When a solution of tuberculin is applied to the eye of a 

 normal individual, no reaction is obtained. If, however, a 

 second instillation is made in the same eye after an interval 

 of seven days, a reaction will be observed in a large propor- 

 tion of cases. This reaction is quite distinct from that 

 previously described as occurring in the eye of the tuber- 

 culous individual. The reaction is rapid in appearance, 

 explosive in type, and subsides with great rapidity. Thus, 

 it is not rare to find, as a result of a second instillation, within 

 from three to four hours after the application, a highly 

 inflamed conjunctiva associated with considerable chemosis 

 of the lids and a profuse purulent discharge. The symp- 

 toms, however, in spite of their severity, rapidly subside. 

 These differences in type of reaction find a satisfactory 

 explanation if we consider the fact that in the tuberculous 

 reaction we are dealing with what may be termed a phenom- 

 enon of general sensitization. In this case the cleavage 

 of the tuberculin introduced within the conjunctival sac 

 is brought about through the action of the proteolytic 

 30 



