TRICOPHYTON TONSURANS 



683 



a large percentage (42 in France, [in London, according to Colcott Fox, 38]) 

 of the scalp Tricophytoses of children. 



1. Microscopical appearance. After treating with potash (p. 690) or dis- 

 sociating in a drop of acetic acid and mounting in glycerin, the affected hair 

 will be seen on examination under the microscope to be filled with numerous 

 spores (pseudo-spores p. 691) : it is uncommon to find filaments. The 

 parasite can be recognized by the following characters : 



(a) The pseudo-spores are arranged in chains : they measure 5-6/u, in 

 diameter and in shape are round or cubical with blunted angles. 



(b) The whole of the hair is infected with the mycelial spores. 



(c) The mycelial filaments show at the most two bifurcations, the " tarsal " 

 appearance is never seen (p. 691). 



(d) The parasite is entirely within the hair. 



(e) The mycelium can only be broken up and then with difficulty in a 1 in 

 40 solution of potash (resistant mycelium). 



2. Cultural characteristics. Tricophyton tonsurans forms a continuous 

 cream-coloured felted mass on the surface of the medium on which it is 

 growing, with fine thread-like prolongations radiating from the centre to 

 the periphery. On maltose-agar the centre of the growth is depressed in 

 the form of a flat-bottomed cupule, the inner sides being perpendicular the 

 outer sloping [T. crateriforme]. On beer- wort agar (one-half) it forms a 



