MICROSPORUM RINGWORM 167 



are definitely produced by a fragmentation of the mycelium, and as 

 a result appear in regular parallel rows or chains. 



Ringworm due to members of the genus Microsporum is some- 

 times referred to as microsporosis, to distinguish it from ringworm 

 caused by Trichophyton. Microsporosis is in the majority of cases 

 a ringworm of the scalp, called tinea capitis by the dermatologists. 

 It occurs most frequently in children; in stubborn and untreated 

 cases caused by Microsporum Audouini it may persist for some years, 

 but usually disappears at puberty. It is the most contagious of the 

 ringworms. During epidemics such as those recently seen in several 

 cities in eastern United States M. Audouini causes a very high per- 

 centage of ringworm of. the scalp. In other parts of the United States 

 M. Canis is of more frequent occurrence and may exceed M. Audouini. 

 In infections caused by M. Audouini the lesion consists of a red- 

 dened scaling area which tends to spread in the characteristic ring 

 form. A number of such patches may form and coalesce to give an 

 irregular area. There is marked scaling of the epidermis. The hairs 

 tend to break off transversely at a height of 2 to 6 mm., leaving the 

 stumps somewhat thickened, whitish, and opaque. Thus there appear 

 a number of very characteristic irregular (moth-eaten) bald patches 

 covered by the short stumps of the diseased hairs, which are fairly 

 uniform in height. Generally inflammatory reactions are not pro- 

 nounced. In infections caused by M. Canis inflammatory reactions 

 are more often present. One can therefore frequently predict, from 

 the clinical appearance, which of the two fungi is the cause of the 

 lesion, but there are so many exceptions to the general rule that it 

 is not a dependable method of determining the etiology. 



The diagnosis may be established by examining an epilated hair 

 in a drop of sodium hydroxide solution. There will be found on the 

 outside a sheath of spores closely packed together to form a poly- 

 hedral or mosaic pattern, and in the interior of the hair shaft septate- 

 hyphae which tend to break up into arthrospores toward the distal 

 end of the hair stub, and which terminate in growing hyphal tips 

 (frequently dichotomously branched) toward the root of the hair. 



The spores germinate readily on Sabouraud's medium and give rise 

 to a rather fine septate mycelium. After a few days the mycelium 

 becomes distended here and there, the swollen cells developing into 

 chlamydospores. These are very characteristic of the mycelium of 

 Microsporum. The aerial mycelium is frequently peculiarly twisted, 

 and gives rise to numerous lateral branches of short length and 

 finally, on some of the branches, clavate conidia borne as lateral 

 buds on conidiophores or undifferentiated hyphae. In M. Canis 



