114 CLINICAL BACTERIOLOGY AND HjEMATOLOGY 



Process. — Prepare the fragments of hair as before, rejecting the 

 free portions. Place them on a slide, add a drop or two of liquor 

 potassae, and apply a cover-glass. Allow the liquor to act for a 

 quarter of an hour or twenty minutes. 



Now place a large drop of dilute spirit at one edge of the cover- 

 glass, and a piece of blotting-paper at the opposite edge ; this 

 will suck up the potash, and the spirit will run in and replace it. 

 After a few minutes lift over the cover-glass, and wash the hairs 

 gently in more spirit. This will harden them. Dry. If epithelial 

 scales are being examined, they may be fixed to the slide or cover- 

 glass by heat in the usual way. 



Stain in aniline gentian violet for half an hour or less. 



Pour off the stain, blot gently, and pour on Gram's iodine 

 solution. Allow this to act for five minutes. Blot again. 



Decolorize with aniline oil, pouring it off and applying a fresh 

 lot from time to time. The process may take an hour or more, 

 and the specimen should be left under the microscope and' ex- 

 amined occasionally. 



When the decolorization is complete {i.e., when the colour is 

 seen to be present in the fungus only), blot gently, and wash 

 thoroughly with xylol. Mount in balsam. 



The specimens are to be examined under a ^-inch objective. 

 A higher power is unnecessary. 



There are certainly three, and possibly more, species of ring- 

 worm which occur in England, and the fungus of favus is closely 

 allied, and is demonstrated by the same process. 



The Microsponn Audouini is the most common species of ring- 

 worm fungus in this country, being responsible for about 80 or 

 go per cent, of all cases. It is a small-spored fungus, and it may 

 be distinguished by the fact that its spores are arranged in an 

 irregular mosaic, and not in chains. Its mycelium, which consists 

 of oblong segments, the length of each of which is about three to 

 six times as great as its thickness, lies in the interior of the hair 

 whilst the spores form a thick mass outside (Fig. 25, and Plate VI., 

 Fig. 4). This sheath of spores projects a short distance above 

 the surface, and may often be seen with the naked eye. The 

 outside of the hair is destroyed, and the surface of the hair 

 eroded ; the former feature serves to differentiate it from all other 

 varieties of ringworm, and from favus. 



This fungus commonly attacks the scalp in children, and in them 

 it usually dies out spontaneously about the age of sixteen, whilst 



