DERMATOPHYTOSIS OF THE FEET 173 



of these are Trichophyton gypseum, T. inter digitale, T. pedis, and 

 T. niveum. This represents a considerable range in colony type, but 

 when many strains are compared intermediate types can be demon- 

 strated readily." The fungi of this group seem to be actually vari- 

 ants of a single species. The oldest name for this species is T. menta- 

 grophytes and this is accepted here as the valid name.^ 



The members of this group will readily infect guinea pigs. They 

 have been found causing infections of various domestic animals, espe- 

 cially horses but also cats and dogs. 



The large-spored ectothrix species are also divided into two groups, 

 those with downy colonies, and those with faviform (i.e., resembling 

 T. Schoenleini) colonies. This difference is due to the amount of 

 aerial hyphae, which is formed early and abundantly in the former, 

 later and less abundantly in the latter. The colonies of the faviform 

 group have the waxy appearance of those of the favus parasite. 

 Cultures of the downy type produce conidia as the only fruiting 

 bodies; cultures of the faviform type fail to produce these, forming 

 only mycelium and chlamydospores. 



All the large-spored ectothrix species may produce ringworm of 

 the smooth skin, scalp, or beard. They occur more commonly in 

 adults than children. They also occur on a variety of domestic ani- 

 mals. The most important species, T. javijorme, is a pathogen of 

 cattle which readily attacks man. 



Tinea Imbricata. Trichophyton concentricum is the etiological 

 agent of a variety of ringworm occurring in China, the Malay penin- 

 sula, various Pacific islands, and in Central America, known as 

 Tokelau ringworm or tinea imbricata. The concentric rings so char- 

 acteristic of the tineas reach their highest development in this disease. 

 There is much more scaling of the epithelium than in the other ring- 

 worms, and as a result there is produced on the skin a complicated 

 pattern caused by the confluence of concentric rings of scales. 



The fungus grows within the epithelium between the superficial 

 and deeper laj'ers. It appears in the scales much as does Epi- 

 dermophyton. Cultures are obtained with great difficulty, partly 

 because many of the very numerous hyphae which can be demon- 

 strated in the scale seem to be dead, and partly because the bacterial 

 infection of the scales is usually so high. The scales can be soaked 

 first in 70 per cent alcohol and a large number of plants made. The 

 colonies are at first like those of T. Schoenleini. Few spores are 

 formed in cultures. 



Dermatophytosis of the Feet. During recent years dermatophy- 

 tosis of the feet (athlete's foot) has attracted increasing atten- 



