576 A MANUAL OF BACTERIOLOGY 



inverted over a Petri dish containing solidified maltose 

 agar. A sharp tap or two is given to the tube, sufficient 

 to cause the spores to drop, and the dish is re-covered. 

 A growth of the organism from single isolated spores thus 

 ensues, and pure cultures can be obtained (Blaxall). 



The various forms of the ringworm fungi can be differen- 

 tiated by cultures, but it is necessary when comparing 

 them to employ media of identical composition, because 

 slight differences in the latter are liable to induce marked 

 changes in the characters of the cultures. A favourite 

 medium, used by Sabouraud and by Blaxall, is maltose 

 agar : 



Peptone . . . . .0-5 grm. 

 Maltose . . . . .3-8 grm. 

 Agar-agar . . . . .1-3 grm. 

 Water 100 c.c. 



Blaxall found that different samples of maltose mate- 

 rially influenced the characters of the cultures. 



Characters of the cultures. Cultures are incubated at 

 30 C. The colonies of the Microsporon do not show any 

 growth until about the seventh day ; little white downy 

 tufts then appear. The fully developed growth on maltose 

 agar forms a large white downy patch with a small central 

 boss ; on potato white downy patches appear with brown 

 discoloration. 



The endothrix variety commences to grow in six or 

 seven days, and on maltose agar in about a month forms 

 a rounded patch with a central crateriform depression, 

 the whole being dusted with fine white powder (Fig. 54) ; 

 on potato, powdery stars develop tinged with yellow and 

 usually without discoloration of the medium. 



The cultures of the ectothrix form are variable. They 

 commence on the third or fourth day ; some develop 

 whitish smooth or wrinkled growths ; others, from the 



