RINGWORM. II5 
mosaic and not in chains (fig. 20). It does not invade 
the interior of the hair, but forms a sheath of spores and 
mycelium outside the submerged portion of the hair; 
this sheath projects for a short distance above the sur- 
face of the scalp and may be seen with the naked eye. 
This fungus usually attacks the scalp in children. 
It is very rare in adults, and it rarely attacks other 
regions than the head. It is thought by some to be 
always caught from a human case of the disease, but 
there are reasons for thinking that it may be derived by 
infection from the horse or cat. 
Fic. 21.—Trichophyton endothrix. 
The most important clinical fact about the micro- 
sporon Audouini is that ringworm caused by it is 
extremely intractable and may run a prolonged course 
in spite of the most skilful treatment. 
The trichophyton endothrix attacks the interior of the 
hairs, and forms long chains. Its spores are somewhat 
larger than those of the preceding species, but the 
difference is not great; the organism is most easily 
recognised by the chain-like arrangement of its spores, 
12 
