TRICHOPHYTONEAE 443 



of infection. Growth is so slow, however, that Sabouraud reports a ease of 

 a man of 80 still showing- active lesions at the border of his hair although the 

 disease was contracted in infancy. The process of scar formation is never 

 fast enough to eradicate the fungus completely. 



While in some cases favus seems confined to the scalp, in others it spreads 

 to the glabrous areas. It appears for a time as circular areas with deep red 

 margins (a phase present but brief and usually overlooked in the hair). It 

 may soon disappear spontaneously and completely, or it may give rise to 

 favic scutula if the resistance of the host is slight. If scutula develop, the 

 lesions will not disappear Avithout treatment but will continue to increase in 

 size, become confluent, and form huge crusts unless they are removed by 

 friction of the clothing or by scratching. Sometimes favus remains localized 

 for a long time on one portion of the body, the scrotum being a common site, 

 where the scutula grow quite rapidly. Patients exhibiting generalized infec- 

 tion often seem to be mentally deficient, generally showing an inferiority 

 complex. 



Finally, favus rarely attacks the nails (1-3% of favus cases). The lesion 

 begins by showing lenticular maize yellow spots analogous to ungual psoriatic 

 lesions. These spots are thickenings of the nail formed by the stratified scales 

 with numerous hyphae. Then the external layers crack and the nail substance 

 becomes friable, scales off, and leaves the nail deformed. Sometimes the ex- 

 ternal layers are more resistant. In this case the nail is uniformly thickened 

 and undergoes a caseous degeneration. The nail is elevated above its bed or 

 the invaded parts remain dry and are eliminated as a powder. The fungus 

 grows only in the horny layer, never penetrating the epidermal cells below 

 the homy layer. 



In South Africa, a favoid condition of the scalp needs further study. This 

 condition, generally known as wit kop, dikwakwadi, or white head, seems con- 

 fined to the syphilitic native, particularly in British Bechuanaland. The con- 

 dition begins as slightly raised isolated macules irregular in distribution with- 

 out reference to hair follicles. They pass from papule to pustule with very 

 little inflammation. By the time the pustule has developed, coalescence has 

 begun. The crust is dry and friable. It seems to develop in layers which are 

 added to from below. These are firmly bound together and do not become 

 detached as in impetigo. Their color is dirty white, but may be dead white 

 or in old cases have a yellowish tinge. The hair soon suffers ; it becomes dry, 

 brittle, and lustreless, and then falls. The condition involves the whole scalp, 

 except the fringe about the neck and in front of the ears. The surface of the 

 crust may be smooth or undulating, the outer laj^ers friable, the inner firmly 

 adherent, attached to the scalp, often stony hard. When the crust is raised, 

 a red noninflamed denuded surface is revealed, practically devoid of serous 

 or sanguineous exudate. There is no local irritation. It is said to be con- 

 fined to heredosyphilitie cases (Fraser 1922). The etiology is still in question, 

 Fraser attributing it to Treponema pallidnm, while Mitchell & Robertson (1915) 

 attribute it to Achorion. 



