292 TUBERCULOSIS 



solution is placed in the conjunctival sac and the fluid allowed 

 to spread over the surface ; for children about half this quantity 

 is sufficient. In the case of a positive reaction the ocular con- 

 junctiva is congested, the lids become somewhat swollen and 

 their inner surface presents a bright red colour, there is increased 

 secretion of tears and a varying amount of fibrinous exudation. 

 The reaction usually reaches its maximum in from six to ten 

 hours after the instillation, and commences to pass off in from 

 twenty-four to thirty-six hours, — in children a little sooner. 



The general results obtained by these two reactions appear to 

 correspond closely. A distinct positive result obtained by either 

 is nearly conclusive as to the presence of a tubercular lesion. 

 In cases of latent tuberculosis the reaction is sometimes obtained, 

 sometimes not. Again, in very advanced cases of tuberculosis, 

 especially a short time before death, a negative result may be 

 got ; in some of these cases v. Pirquet has met with a colourless 

 papule or a livid spot without exudation, conditions which he 

 describes as indicating a "cachectic reaction." The ophthalmo- 

 reaction is the more easily applied, at least in adults, but its use 

 is contra-indicated when there is any abnormal condition of the 

 conjunctiva. Even apart from this, however, inflammatory 

 symptoms of disagreeable severity sometimes supervene. It 

 should also be noted that a second test ought not to be applied 

 to the same eye; as the first may produce a condition of super- 

 sensitiveness (p. 290). Von Pirquet claims for his method that 

 in the case of children it can be satisfactorily carried out with 

 greater ease than the ophthalmic test. 



It will be recognised that the processes underlying the original 

 tuberculin reaction on the one hand, and the cutaneous and 

 ophthalmic reactions on the other, are analogous. In the former 

 there is the occurrence of local inflammation with metabolic 

 changes and fever ; in the latter, of mild inflammatory effects, — 

 in both cases the phenomena being found only in tubercular 

 subjects. 



The Use of Old Tuberculin in the Diagnosis of Tuberculosis in CalUe. — 

 In cattle, tuberculosis may be present without giving rise to apparent 

 symptoms. It is thus important from the point of view of human 

 infection that an early diagnosis should be made. The method is 

 applied as follows : The animals are kept twenty-four hours in their 

 stalls, and the temperature is taken every three hours, from four hours 

 before the injection till twenty-four after. The average temperature in 

 cattle is 102 "2° F. ; 30 to 40 centigrammes of tuberculin are injected, and 

 if the animal be tubercular the temperature rises 2° or 3° F. in eight to 

 twelve hours, and continues elevated for ten to twelve hours. Bang, who 

 has worked most at the subject, lays down the principle that the more 

 nearly.the temperature approaches 104° F. the more reason for suspicion 



