HYPHOMYCETES 



639 



moisture is present. In laboratories they are frequently found as con- 

 taminants, and in order to procure them for purposes of study it is only 

 necessary to expose agar or gelatin plates in a dusty, dark corner. In 

 households they are frequently found growing in store-rooms upon stale 

 bread, shoes, leather trunks, and on remnants of food. Most of them 

 prefer an acid environment and are dependent upon a free supply of 

 oxygen. At room temperature they grow more readily than at the 

 usual incubator temperature. 



DISEASES CAUSED BY HYPHOMYCETES 



Pityriasis versicolor (Microsporon furfur). — Pityriasis is a disease 

 of the skin observed chiefly among persons living under conditions of 

 uncleanliness, or among those who combine these conditions with a 

 tendency to profuse perspiration. It begins 

 as a small, light brown or yellowish patch 

 upon the skin of the abdomen, breast, or 

 back, is flat and barely raised from the cuta- 

 neous surface. It spreads and coalesces with 

 similar spots until the entire area resembles 

 strongly the figures of a map with irregular 

 continents and islands. The disease does 

 not penetrate into the skin itself, but consists, 

 as Plant has pointed out, of a simple sapro- 

 phytism of the inciting agent upon the skin. 



The condition is caused by a member of 

 the group of Hyphomycetes, discovered in 

 1846 by Eichstedt, and later named Micro- 

 sporon furfur. The microorganism consists 

 of a dense meshwork of mycelial threads, 

 from which septate hyphae arise in large 

 numbers. From the ends of these, spores 

 arise in rows, after the manner depicted for 

 penicillium (Fig. 149). The hyphae, accord- 

 ing to Unna,i show a characteristic bending at right angles, due to 

 a slight flattening of their diameters. Characteristic of the micro- 

 sporon proper, in preparations made from cutaneous scrapings, are 

 the fragments of bent hyphae and the large numbers of free spores. 



Fig. 148. — Mucor eamo- 

 sus. Ripe sporangia on 

 columella. (After Lindt.) 



' Unna, "Histopathol. of Skin," transl., N. Y., Macmillan, 1896. 



