RINGWORM. 117 
This fungus is a rare cause of ringworm of the scalp, 
and the disease it causes is readily cured. It also 
causes ringworm of the body and of the beard region, 
which the endothrix does not attack. According to 
Sabouraud (to whose work on these organisms we owe 
most of our knowledge on the subject) kerion is always 
caused by this organism, but this is not generally 
accepted. It appears, however, to be a fact that sup- 
purative lesions (folliculitis, kerion, &c.) are usually 
caused by this fungus. 
This species is often derived from one of the lower 
animals, especially from the horse, cat, and dog. 
Favus is caused by a closely allied organism, the 
achovion Schénleiniti. This may be demonstrated by 
either of the processes already described. It consists 
of mycelial threads which are not continuous, but are 
composed of short rods. The whole has an appearance 
which has been compared to that of the metatarsal 
bones, and this resemblance is increased by the fact 
that sometimes several filaments radiate from one point, 
forming the “ favic tarsus.” 
The identification of the variety of organism which is 
present does not usually present great difficulties. The 
first point to be looked to is the arrangement of the 
spores. If these are present in an irregular mosaic the 
microsporon is present; if they form filaments some- 
what resembling those of a streptococcus the organism 
is a trichophyton. To settle which it is look to see 
whether the cuticle is present, and whether the fungus 
invades the interior of the hair. This can usually be 
determined by focussing up and down until you see an 
‘‘ optical section” of the hair in question. It is impor- 
tant not to be deluded by the fact that the fungus which 
lies on the outside of the-hair will appear to be inside it 
if a surface view only is taken. 
