116 An Introduction to Medical Mycology 



Only once have we been able to isolate T. purpureum from the surface 

 of a nail obviously infected by fungi and never from a nail with no clinical 

 evidence of fungous involvement. In connection with these observations 

 we wish to point out that scrapings from the surface of an infected nail 

 frequently contained the ordinary saprophytes but that when scrapings 

 from the deeper portions of the nail were planted on agar slants, T. pur- 

 pureum in pure culture resulted. For this reason cultures of infected nails 

 should be taken from different depths in the nail substance. Unless the 

 deeper portions are examined (and even when they are) a number of 

 scrapings may be required before the organism can be cultured. 



Infection of a fingernail should always invite examination of the toenails, 

 since the two sites are frequently simultaneously affected. In onychomycosis 

 caused by T. gypseum and also when T. purpureum is the pathogen the 

 toenails are involved more frequently than the fingernails in the ratio of 

 11:1. 



c. Involvement of other regions. It should be noted that lesions attrib- 

 utable to T. purpureum may appear on the glabrous skin, on the upper 

 parts of the thighs and in the inguinal and perianal regions, and occa- 

 sionally the organism produces infection of the hair follicles. Peculiarities 

 of the infection in these locations have been considered in the sections on 

 tinea sycosis (pp. 75 ff. ), tinea glabrosa (pp. 78 ff. ) and tinea cruris 

 (pp. 93 ff. ). Thompson and others have offered experimental proof that 

 thromboangiitis obliterans is caused by infection spreading from the feet 

 and due to T. purpureum. Reiss and Graham failed to reproduce the 

 disease in animals and at this time the question of causal relationship must 

 be considered not settled. 



(f ) Dermatophytid.— This subject was briefly considered in the section 

 on tinea capitis (pp. 47 ff. ). The term dermatophytid is probably better 

 than trichophytid, since allergic rashes due to Microsporum may be clin- 

 ically indistinguishable from those due to Trichophyton. Guth, Bloch, W. 

 Jadassohn, Peck and others have contributed to our knowledge of these 

 rashes. It has been stressed by Bloch, Jadassohn and their school that 

 allergy or an acquired specific sensitization is an invariable accompani- 

 ment of the rash. The eruption was at first thought to follow deep infec- 

 tion only, being considered due to dissemination of the products of fungi 

 through the blood stream. Williams was the first to show that secondary 

 eruptions may follow infection of the interdigital webs, and he later also 

 found that macerated tissue in the groin max act in a similar way as the 

 focus for a secondary rash at a remote point. The suggestion that nails 

 may act in like manner as a focus for direct dissemination of the products 

 of fungi through the blood stream lias not been confirmed. It is notable 



