682 THE PARASITES OF RINGWORM 



organisms. The following is the method advised by Sabouraud for isolating 

 the parasite of ringworm from a diseased hair : 



Break off one of the affected hairs, lay it on a sterile slide and, with a 

 sterile cutting needle, divide it into as many pieces as possible. Sow each 

 fragment on a tube of agar (beer- wort or Sabouraud's) containing a large 

 percentage of maltose a medium on which the other organisms accompanying 

 the tricophyton grow badly. As soon as growth is visible, as indicated by a 

 downy-looking speck at the site where the fragment of hair was sown, sub- 

 cultivate on to another tube of the same medium ; after sub-cultivating two 

 or three times in this way transfer a portion of the growth from the third or 

 fourth sub-cultivation when about 20 days old to a slice of potato, rubbing it 

 well over the surface of the medium. In this way single colonies are obtained. 

 The various cultures should be grown at the temperature of the laboratory. 



Krai's method (p. 691) is also useful. The technique is more delicate but results 

 are obtained more quickly than by Sabouraud's method. 



Plaut advises laying the hair on a sterile slide, covering it with a cover-glass and, 

 after fixing the angles of the latter with a little drop of wax, placing the preparation 

 in a moist chamber. After about a week some of the spores will have germinated 

 and produced a mycelium which can easily be collected for sowing culture media. 



When sub -cultivating it is essential to pick up only a small portion of the 

 growth, and for this purpose it will be found more convenient to use a steel 

 needle than the ordinary platinum wire. 



3. Experimental inoculation. The tricophyta are pathogenic for man and 

 the lower animals. The results of these experimental infections will be 

 described when dealing seriatim with the different species. 



[4. Classification of the Tricophyta. The parasitic species of the genus 

 tricophyton are divided into two large groups : 



[1. Tricophyton endothrix. 



[2. Tricophyton endo-ectothrix (or ecto-endothrix). 



[Pathogenically, the endothrix species are confined to the inside of the 

 hair, while the endo-ectothrix species grow both within and around the 

 affected hair. The former are human parasites and infection takes place 

 from man to man. The latter are invariably of animal origin ; man becomes 

 infected by contact with a diseased animal, and the source of the infection is 

 generally easy to trace. 



[The endo-ectothrix species are sub-divided, according to the size of the 

 " spores " of the parasite, into Ectothrix microides and Ectothrix megaspores 

 and in each of these sub -divisions there are varieties or species differing from 

 one another in cultural characteristics. The small-spored endo-ectothrix 

 species give either a white, plastery-looking growth (T. gypseum) on the 

 maltose test medium, or a white, downy growth (T. niveum). The large- 

 spored endo-ectothrix species give either a velvety growth or a culture like 

 the parasite of favus. 



[The table on p. 683 modified from Guiart exhibits these points in tabular 

 form.] 



[A. Endothrix species.] 

 1. Tricophyton tonsurans (Malmsten). 



Syn. Tricophyton megalosporum endothrix Sabouraud ; [T. crateriforme 



Sabouraud.] 



Tricophyton tonsurans grows inside the hair. The affected hair breaks 

 off very short (3-4 mm. from the skin) is thicker than the uninfected hair 

 and has no ring or collar encircling it. The hairs are very difficult to epilate 

 and are occasionally decolourized. Tricophyton tonsurans is responsible for 



