HYPERSUSCEPTIBILITY IN MAN 241 



medium favorable for proteolysis in and about the tubercle. Digestion 

 and the liberation of toxic material result and are reflected in the con- 

 stitutional effects. In the non-tuberculous individual it is probable 

 that the primary serum alterations also occur, but the digestive ferments, 

 finding- no focus to attack, liberate no toxic material and no general 

 reaction is elicited. Any agent that brings about a f erment-antif erment 

 ratio favorable for proteolysis will effect a general reaction provided 

 the focus be sufficiently unstable. Conditions such as pregnancy, acute 

 infections, protein shock, in which there is an increase of antiferment, 

 will inhibit the reaction. In late stages of tuberculosis there is also 

 increased antiferment and therefore less marked local reactions but 

 more marked general reactions. 



Specificity of the Tuberculin Reaction. The tuberculin tests have 

 probably been more carefully controlled by autopsy than any of the 

 other clinical tests, and we therefore are able to state with considerable 

 assurance that a positive reaction indicates the presence of tuberculosis 

 in the vast majority of cases, but, on the other hand, gives no very 

 precise information as to the degree of activity of the process. Factors 

 of error are more particularly found in the personal equation of the 

 examiner. Leprosy and actinomycosis, however, may give confusing 

 results. In a very large series of tests, more than 15,000, the percentage 

 of error is very small, varying from 2 to 3 per cent. Negative reactions 

 may appear in markedly active tuberculosis, in the very early stages of 

 the infection, in those small cicatrized lesions of the lung so firmly 

 encapsulated that no absorption takes place, during continued treatment 

 with tuberculin; also during the course of measles, typhoid fever, 

 acute articular rheumatism, pneumonia, diphtheria, pertussis, serum 

 disease and during pregnancy. 



Some authors have such confidence in the specificity of the tuber- 

 culin reaction that they consider it possible to determine the strain of 

 the organism concerned, but others deny that this delicacy is attainable. 

 The recent work of Petersen would indicate that there is a large non- 

 specific element in the tuberculin reaction. Tuberculous patients may 

 react to the following substances with local and even general reactions : 

 hypertonic salt solution, distilled water, iodides, some colloidal metals, 

 protein split products, etc. Non-tuberculous individuals will tolerate 

 equal doses without reaction. The relation of this type of reaction to 

 the true test has been indicated in discussion of the theories of the 

 tuberculin test. 



Utility of the Tests. At the present time in clinical practice the 

 subcutaneous or general reaction is not very widely employed, because 

 of the prejudice that has been aroused by the possibility of exciting the 

 lesion to renewed activity. Similarly a prejudice exists somewhat 

 unjustly against the use of the conjunctival reaction. Although Ham- 

 man and Wolman indicate that the intracutaneous test is the most sensi- 

 tive, our observation is to the effect that the cutaneous test is most 

 widely employed. It is simple, free from danger, well controlled, 

 16 



