176 INFECTIONS CAUSED BY MOLDS 



use of the name Epidermophyton for other species found on the feet, 

 merely because they are not seen in hairs, is incorrect. E. floccosum 

 is found on the feet as a cause of athlete's foot but it is most im- 

 portant as the cause of tinea cruris or eczema marginatum. It oc- 

 curs on the smooth skin in those parts which are likely to be moist, 

 most frequently the inner surfaces of the thighs, but also in the 

 axillae, the folds of the buttocks, or under the breasts. It is more 

 frequent in warm climates and is especially prevalent in India, 

 where it is apparently one of the conditions known as dhobie itch. 

 It has been responsible for epidemics aboard ship. The afTection is 

 somewhat different from the other ringworms especially in that it 

 does not tend to heal in the center as it spreads at the periphery. 



The fungus is found in scales of epidermis as septate hyphae break- 

 ing up into chains of oval or round arthrospores. In artificial cul- 

 tures, reproduction takes place entirely by macroconidia, which are 

 not spindle-shaped as in Microsporum, but are clavate or egg-shaped. 

 The walls are thick and smooth. The distal end is rounded. The 

 macroconidium may be one-celled or may have one or more septa. 

 No small conidia are produced. The color of the colony is a char- 

 acteristic greenish yellow. Cultures rapidly become overgrown with 

 the white sterile mutant mentioned earlier. 



Saprophytic Skin Fungi 



Pityriasis Versicolor. Pityriasis versicolor is one of the common- 

 est of the dermatophytoses. It is characterized by a brownish dis- 

 coloration of the skin and it occurs most frequently on the trunk. 

 It causes a light branny scaling and, in some cases, slight itching. 

 In non-pigmented areas of the skin the lesion is darker than the 

 surrounding skin. In exposed skin which is tanned the lesion is 

 often lighter than the other skin, apparently because the fungus 

 interferes with the normal sun-tanning. 



The causative organism, Malassezia furfur, may be found in 

 large numbers in scales of the epidermis mounted in hydroxide solu- 

 tion. It appears as short irregular strands of branched hyphal frag- 

 ments accompanied by large numbers of round spores varying con- 

 siderably in size. When stained with carbol fuchsin the spores are 

 seen to contain several deeply stained bodies of globular form in a 

 less deeply stained protoplasm. The spores tend to be arranged in 

 clusters aud are perhaps produced from the hyphae as spores. 



