PINK TORULA 449 



glycerine, 0*25 per cent, of asparagin, and 8 per cent, of 

 gelatine. Several other varieties of light-giving bacteria 

 are known. They all, generally speaking, grow best at a 

 low temperature. 



Pink Torula {Saccharomyces rosaceus). — This organism ia 

 very common in air, dust, etc. It is a slightly rounded or 

 oval yeast, the cells ranging from 5 to 8 /i in diameter, 

 which, under the microscope, are seen to contain a delicate 

 yellow pigment, but appear of a pink colour when seen in 

 the mass. Cultural characters : 



Gelatine Tubes. — Small white or grayish points are seen 

 along the line of inoculation, which afterwards gives rise 

 to a coral piak mass. 



Potatoes and Bread. — A bright coral pink growth forms. 



Bacillus Prodigiosus. — This organism is common in the 

 air, dust, etc. It is a very short bacillus, that differs some- 

 what in size, the largest organisms being about 1'7 /* long 

 by 1 /i broad. They are frequently seen in pairs, and are 

 non-motile. The organism grows well on all the ordinary 

 media. The production of the blood-red colour is governed 

 by the temperature and by the presence of oxygen, as well 

 as by the nature of the nutrient medium. The colour 

 decreases in cultures kept at incubation temperature. By 

 long-continued growth on artificial media, the organism 

 often loses its power of pigment production, which may, 

 however, often be restored by cultivation on potatoes. 

 Cultures give off an odour of trimethylamine. Cultural 

 characters : 



Gelatine Plates. — After two days the colonies are visible 

 as circular depressions, each having a red centre. The less 

 developed colonies in the depth are seen to be devoid of 

 colour. 



Gelatine Tubes. — The growth is very rapid, the gelatine 



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