Immunity and Cutaneous Sensitization 33 



cutaneous sensitivit) to the vaccine. We consider this an important observa- 

 tion, since it has been the experience <>l a number of investigators that the 

 initiation of cutaneous sensitivity to fungi is only possible when the living 

 organism invades the living tissues. The results of our tests seem to confirm 



this opinion. Tn another report it was noted that occasionally a tendenex to 

 a response 1 had developed 48 horns after an initial delayed response to 

 trichophytin. It was undecided, however, whether this tendency could be 

 elassified as initiation of sensitivity. 



(h) Graded trichophyton tests.— A small percentage of patients do not 

 react to trichophytin even in concentrated solution (1:10 or undiluted), 

 and another small group react to a highly dilute 1 solution (1:300). In 

 neither of these groups, which we have studied, do the patients have well 

 defined clinical peculiarities or family histories of allergy, and we are 

 unable to account for their different responses or as yet to attach any 

 significance to the finding. With the largest number of persons trichophytin 

 undiluted or in concentrated solutions (up to 1:10) is primarily an irritant, 

 and more dilute solutions are requisite for determination of hypersensitivity 

 or the lack of it. The optimal dilution varies somewhat with the product. 



(i) The patch test with trichophytin.— It has been known for a num- 

 ber of years that some persons react to a patch test with trichophytin. This 

 has led to the belief that some of the eczematous eruptions on the hands 

 may be toxic fungous eruptions ( dermatophytids ) or that the infection 

 may be primarily eczematous, simulating contact dermatitis. Our studies 

 in regard to this point are as yet incomplete, but from our observations to 

 date we conclude that both possibilities must be uncommon. In our experi- 

 ence the patch test with trichophytin has less significance than the intra- 

 cutaneous test. Even in cases of undoubted dermatophytid the patch test 

 with trichophytin frequently shows a negative reaction. This may be inter- 

 preted to mean that in these rashes the epidermis is not the tissue pri- 

 marily sensitized. 



(j) Does the site of injection of trichophytin influence the size 

 OF the response?— When the arm, the leg and the abdomen were used 

 for test sites no appreciable difference was noted in the size of the reaction, 

 nor did we find one site reactive when one or more of the others were non- 

 reactive. In some instances a moderate increase in the size of a reaction was 

 noted when skin adjacent to an active fungous infection was tested and the 

 reaction was compared with that in skin at a remote point. This, however, 

 was not invariable, and we have even noted a diminution in the size of the 

 reaction near an active fungous focus. In routine practice the upper, outer 

 arm is the usual test site. 



(k) Reliability of the [ntractjtaneous test with trichophytin.— We 



