468 BIOLOGY OF PNEUMOCOCCUS 



history of previous pneumonia, the test was positive in 56 per cent 

 of the subjects tested. In the case of individuals having a history 

 of pneumonia in the past, 15 per cent of the subjects reacted, 

 while in convalescent patients only 5 per cent exhibited positive 

 reactions. Coca reported that not all filtrates tested were anti- 

 genic and, at the time, ventured no statement concerning the type- 

 specificity of the phenomena. 



Recently Coca, 246 after a further study of the alleged pneumo- 

 coccal toxin, stated that the action of the toxin in the skin was 

 type-specific and, furthermore, that the toxin was not the type- 

 specific polysaccharide. 



The application of the skin test as a guide to serum therapy 

 and as a prognostic aid was suggested by Francis (1933). 473 All 

 but one of the patients who had recovered from Type I Pneumo- 

 coccus pneumonia (the great majority of them had received spe- 

 cific antipneumococcic serum) gave an immediate reaction to the 

 Type I polysaccharide at about the time of recovery. Francis 

 claimed : 



The test has distinct advantages over the agglutination reaction in 

 that it is not merely an index of circulating antibodies. When positive, 

 it invariably denotes that recovery has begun; when negative, it indi- 

 cates further serum therapy. The mechanism of the positive skin test is 

 closely related to that operative in recovery from pneumonia, and is ap- 

 parently the resultant of antibody and tissue activity. 



THE MECHANISM OF DERMAL ALLERGY 



In addition to the foregoing discussion, two studies may be 

 mentioned which have a direct bearing on the physiological or 

 immunological processes operating in the production of the aller- 

 gic state and in the manifestations of the hypersensitive condition 

 as elicited by pneumococcal derivatives. Martin and Hill (1930) 866 

 tested the effect of an alien protein on the reactivity of dermal tis- 

 sues in albino guinea pigs receiving intradermal injections of liv- 

 ing pneumococci. One group of animals received into the skin of 



