TEXT-BOOK OF BACTERIOLOGY. 365 



In the test-tube the trichophyton forms on the surface of the 

 medium a film several millimetres thick, arranged in crusty folds, 

 wliite, as if dusted with flour, its lower surface being of a sulphur 

 yellow color. Only a restricted growth takes place in the lower 

 strata of the gelatin. Liquefaction is less speedy with the favus 

 fungus and the film developed is not quite so thick ; the lower sur- 

 face is of a brighter yellow color. On agar-agar a white and dry 

 film forms and adheres firmly to the medium. 



THRUSH. 



The micro-organism of thrush is the most perfect link between 

 the thread and yeast fungi. Under certain conditions of nutrition, 

 for instance, almost always on the gelatin plate, on very sweet 

 rnedia, etc., it appears in a yeast-like form, as a pronounced sac- 

 charomyces; but under other conditions likewise, for instance, at 

 the bottom of the test-tube cultures, it develops long thread-shaped 

 mycelia. The gelatin is not liquefied. 



The thrush fungus is pathogenic for rabbits, as proved byKlem- 

 perer's investigations. The animals perish from within twenty- 

 four to forty-eight hours after injection of a pure culture into the 

 blood-vessels. The internal organs are traversed by the mycelium 

 grown out into long threads. 



SACCHAROMYCES. 



The common beer-yeast, Saccharomyces cerevisise, is the most 

 widely diffused of the yeast fungi and corresponds to the general 

 description of these organisms. 



Various kinds of yeast fungi have been found in the examination 

 of air. They often appear on the plates as accidental contaminations 

 and are noticable by the color of their colonies. The " red yeast " 

 is the most common; it produces a pale red pigment. The "white 

 yeast" forms snow-white, lustrous cultures. None of them liquefy 

 gelatin; all thrive atordmary temperatures. They do not seem of 

 any special importance and are destitute of the ability of fermenting 

 sugar solutions, as true yeast does. 



ACTINOMYCES. 



The actinomyces (ray fungus), finally, is a peculiar vegetable mi- 

 cro-organism whose classification is still in doubt. 



Whitish, rather compact swellings are sometimes noticed on 

 the jaws of cattle. They spring from the bone, grow rapidly, and 



