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 Plaut 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 iater named Micro- 

 sporon furfur. The microorganism consists 

 of a dense meshwork of mycelial threads, 

 from which septate hyphse arise in large FlG 148 _ MUCOR RAMO- 

 numbers. From the ends of these, spores sus. Ripe sporangia on 

 arise in rows, after the manner depicted for columellse. (After Lindt.) 

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

 ing to Unna, 1 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. 



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

 42 



