TINEA IMBRICATA 



141 



T. mentagrophytes.This is the T. megalsporon endoectothrix of Sabouraud. The 

 external spores are in chains or in short mycelial threads, not mosaics of spores, 

 and are of very unequal size (3 to 15 microns). 



The internal spores are scarce and are from 5 to 6 microns in diameter. To exam- 

 ine pull out downy hairs from the periphery of the lesion rather than the dead 

 central ones. There are varieties from horse, cat, and bird. The lesions are more 

 inflammatory than those of the endothrix class. Most of the beard and body ring- 

 worms belong to this group very few scalp cases. The lesions are often of a pus- 

 tular type. The cultures are finely rayed. 



Some give yellow cultures, others white and one derived from birds a rose-colored 

 culture. 



Microsporum audouini. This is the so-called small-spored ring- 

 worm and is a very common and highly contagious affection of the scalp 

 in children in England and France; less so in other countries. 



It is almost never seen in the tropics. It almost exclusively affects the hairy 

 scalp. The spores are 2 to 3/4 in diameter. The broken stump of the hair is char- 

 acteristic. The fungus is packed as a mosaic of spores, forming a white sheath, 

 chiefly on the outside of the hairs. It gives a downy-white culture. 



Achorion schoenleini is the cause of favus. The cultures are rather 

 wrinkled. It is characterized by the scutulum or favus cup. This is a 

 sulphur-yellow pea-sized cup with a central lusterless hair. Affected 

 hairs may not show a cup. Favus is not so contagious as ringworm. 

 It chiefly affects the hairy scalp, but may also invade the nails and even 

 the body. 



Microscopical examination shows great irregularity of spores and mycelium, the 

 latter being irregularly disposed and of varying thickness and length and wavy 

 instead of straight as in Trichophyton. There is also the greatest irregularity in 

 the refractile favus spores they are gnarled and bizarre shaped, in contrast to the 

 regular ovals or spheres of the ringworm fungus. Cultures show ridges or con- 

 volutions. 



Endodermophyton concentricum. Castellani considers this as the 

 causative fungus of tinea imbricata rather than Aspergillus concentricus . 



It was formerly supposed that the causative fungus was Aspergillus concentricus 

 but Castellani has demonstrated that fungi of this genus, when present, are merely 

 accidental. He has isolated in cultures what he considers the causative fungus, 

 Endodermophyton concentricum. He treated scales for ten minutes with absolute 

 alcohol and then placed single scales in a series of tubes of maltose bouillon. The 

 fungus grows between the rete malpighii and the external epidermal layers forming 

 a network of mycelial threads, about 3 microns broad. 



Another fungus cultured from tinea imbricata scales is Endodermophyton indicum. 

 Inoculation of this organism in pure culture produced the disease. 



The characteristics of the genus Endodermophyton are the growth of a mycelial 



