Il6 BACTERIOLOGICAL DIAGNOSIS. 



and by the fact that they lie within the hair, the cuticle 

 of which usually remains intact (fig. 21). 



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

 worm of the scalp, and the disease caused by it appears 

 to be somewhat 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 or eczema marginatum. 



It always appears to be derived from a human case, 

 and never by infection from animals. 



FIG. 22. Trichophyton ectothrix from a case of kerion. 



The trichophyton ectothrix (like the microsporon) forms 

 a sheath round the outside of the hair, to which it is 

 closely applied, like the bark to a tree. 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 (fig. 22). 



In some cases this organism does tend to invade the 

 hair, and in this case the name " endo-ectothrix " is 

 applied to it. 



