246 An Introduction to Medical Mycology 



cellular accumulations. I have applied the term "mosaic" to this form because, follow- 

 ing as they do the intercellular clefts, the hyphae come to surround smaller and larger 

 polyhedral spaces, which collectively give the "pavement" effect. 



The remarkable fact that this form is seen only in locations and usually 

 in lesions suggesting a fungous origin has not yet been satisfactorily ex- 

 plained. In lesions equally inflammatory or in scaly conditions of the skin 

 remote from the hands and feet it is seldom isolated. Thus in the scales of 

 psoriasis, pityriasis rosea, or seborrheic dermatitis, the mosaic form is 

 unknown. The mosaic fungus may indicate a fungous infection without 

 being of definite fungous structure. 



2. SAPROPHYTES 



If the amount of vegetative fungous material is large, if there is branch- 

 ing, if there is a green or brown tone or if the individual segments are 

 large or of different sizes, one is fairly certain that the fungus is not a 

 pathogen, judicious selection of material after one discards superficial 

 scales or nail tissue will usually obviate the necessity of deciding whether 

 the fungus is a saprophyte or a pathogen. In open lesions, particularly those 

 of long duration, saprophytic fungi may colonize in the diseased tissue and 

 will perhaps produce clinical symptoms. 



3. ARTEFACTS 



Oil and grease, air, hairs, cotton fibers, feathers and many other sub- 

 stances may cause trouble for the novice. One should mount specimens of 

 various artefacts and become familiar with their appearance. The varia- 

 tions in size of the oil droplets or air bubbles stand out in contrast to the 

 relative uniformity in size of spores or yeast cells. With structures such as 

 cotton fibers, examination of the ends will show a ragged or square effect, 

 whereas a fungous filament is always rounded at its ends. Green and 

 Shepard drew attention to the possible confusion with elastic fibers when 

 the specimen is a shaving of skin extending into the cutis. Elastic fibers 

 may be observed at times in pus. The profusion of fibers, the absence of 

 cross-walls, their translucency and the variability in size serve to differen- 

 tiate them from fungi. 



BIBLIOGRAPHY 



Cornbleet, T.; Schorr, H. C, and Popper, H.: Mosaic fungus: An intercellular artefact. 



Arch. Dermat. & Syph. 48:2<S2, 1943. 

 Davidson, A. M., and Gregory, P. II.: So-called mosaic Fungus as an intercellular deposit 



of cholesterol crystals, I. A. M. A. 105:1262, 1935. 



