RINGWORM 143 



This fungus commonly attacks the scalp in children, and in 

 them it usually dies out spontaneously about the age of six- 

 teen, whilst other varieties of ringworm sometimes do not: 

 the latter persist more frequently, though even they are rare 

 in the adult. It is very rare in adults, and it rarely attacks 

 regions other than the head. Nearly all inicrosporon infec- 

 tion is human in origin, but there is also a microsporon of 

 the dog and cat distinguishable in culture (Microsporon canis 

 vel lanosum) which usually affects the glabrous skin more 

 abundantly than does Audouini and is not infrequently 

 slightly inflammatory on the scalp. 



The most important clinical fact about the M. Audouini is 

 that ringworm caused by it is extremely intractable, and may 

 run a prolonged course in spite of the most skilful treatment 

 other than the X-rays. 



The Trichophyton (or Megalosporon) endothrix attacks 

 the interior of the hairs, and forms long chains; it always 

 involves the hair just inside the cuticle. Its spores are some- 

 what larger than those of the preceding species, but the differ- 

 ence is not great; the organism is most easily recognized by 

 the chain-like arrangement of its spores, and by the fact 

 that they lie within the hair, the cuticle of which usually 

 remains intact (Plate VI., Fig. 2). 



This fungus is a rare cause (in this country) of ringworm 

 of the scalp, and the disease caused by it appears to be some- 

 what easier to cure than that due to the microsporon, though 

 opinions on this point are divided. It also attacks other 

 regions of the body, causing- tinea circinata. It is not infre- 

 quently the cause of beard ringworm, and is commonest in 

 ringworm of the nails. 



It is usually derived from a human case. Two species of 

 endothrix attack birds, and may occasionally be communicated 

 to man. 



The T. ectothrix, or, as some call it, ecto-endothrix, forms 

 (like the microsporon) a sheath round the outside of the hair, 

 to which it is closely applied, like the bark to a tree, but, 

 unlike the small-spored variety, does not destroy the cuticle. 

 The spores are about as large as in the preceding- species, and 

 are arranged in chains ; this fact, together with the position of 

 the fungus with regard to the hair, will enable a diagnosis to 

 be made (Plate VI., Fig. i). 



This fungus is a rare cause of ringworm of the scalp, and 



