286 An Introduction to Medical Mycology 



auclouini begins to grow later, the young colony is white rather than yellow 

 and the appearance under filtered ultraviolet rays is dull and mouse-gray 

 rather than bright blue and pink. In the culture mount, fuseaux are rarely 

 found, whereas in the culture of M. lanosum fuseaux are normally present 

 in large numbers. 



2. MICROSPORUM LANOSUM 



This fungus is occasionally seen in Europe. In the United States it is re- 

 sponsible for tinea capitis in about 40 per cent of the cases observed in large 

 Eastern cities and causes the majority of ringworm infections of the scalp 

 in the Southern and Pacific Coast regions. 



(a) Clinical characteristics.— At times the appearance of the patches 

 of the scalp is indistinguishable from the manifestations of M. audouini. 

 Usually, however, there is at least some erythema, and pustulation of mild 

 or of severe degree may be noted. Kerion is present in one of every 30 

 cases. The history of infection is short (a few weeks or several months). 

 Occasionally infection may be traced to an animal; pets (kittens and pup- 

 pies) are sometimes incriminated. 



Infections on the smooth skin are also of common occurrence; they are 

 more frequent in children but are occasionally found in adults also. The 

 lesions are usually circinate, with a clearing center and a vesicular border. 

 Infrequently, widespread infections of the glabrous skin occur. The adult 

 beard is also known to have been affected, although not in our experience. 



(b) Immunologic reactions.— There is usually a moderate or vigorous 

 reaction to the intracutaneous trichophytin test. In rare instances the reac- 

 tion is not present. 



(c) Microscopic features.— The appearance in the sheath around the 

 infected hair is indistinguishable from that of M. audouini in the same loca- 

 tion. The individual spores are small and round and are present in clusters. 

 On the smooth skin, mycelium is noted in sparse amounts. Lanugo hair is 

 sometimes affected. 



(d) Cultural characteristics.— Growth is moderately fast. A downy 

 fluff appears, around which is yellowish pigment. In two weeks the central 

 part of the colony is depressed. The aerial growth is abundant and wooly. 

 The color is a buff-tan. Grooves, if present, are often concentric, although 

 radial grooves are common. Pleomorphism starts with regularity after four 

 or five weeks. Considerable pigment of yellowish color is usually produced 

 in the subsurface portion of the colony. 



(e) Culture mount.— The characteristic feature is the large number of 

 fuseaux of the tapering variety (taken from the center of the growth). Their 



