562 A MANUAL OF BACTERIOLOGY 



Clinical Examination (Pathogenic Yeasts, etc.) 



The cells can be well seen in the fresh state in the teased-up 

 tissues mounted in water or glycerin. 



Curtis recommends staining in carbol-thionine blue, and for 

 sections, picro- carmine. 



Busse's method for sections is as follows : 



1. Hsematoxylin solution for fifteen minutes. 



2. Wash in distilled water. 



3. Counter-stain in weak carbol-fuchsin (1 : 20) for thirty 

 minutes to twenty-four hours. 



4. Decolorise in 95 per cent, alcohol for fifteen seconds to one 

 minute. 



5. Absolute alcohol, xylol, mount in Canada balsam. 

 Gilchrist recommends treating the sections with 10 per cent. 



caustic potash solution and examining in 50 per cent, glycerin 

 without staining. 



Brayton recommends that small pieces of the tissues should be 

 excised from the growing margin, treated with ether for two to 

 five minutes, macerated in 20 to 30 per cent, caustic potash 

 solution for five to ten minutes, and then examined without 

 staining. Cultures may be readily obtained, with a little care, 

 preferably on beer- wort gelatin or maltose agar. 



Fermentation 



The yeasts are of great importance in inducing many chemical 

 changes, especially alcoholic fermentation, beer and wine being 

 almost exclusively due to their activity. 



Taking brewer's yeast, Saceharomyces cerevisice, as a type, the 

 yeast cell is observed to be slightly ovoid in shape, measuring 

 8 to 9 [L in diameter. The protoplasm is granular, contains one 

 or more clear spaces or vacuoles, frequently bright, refractile 

 globules of fatty matter, and is surrounded by a cell wall of 

 cellulose. It has been repeatedly stated that a nucleus is present, 

 but this is doubtful. When the yeast-cell is freely supplied with 

 nutriment, reproduction by gemmation proceeds rapidly, and a 

 whole string of cells may form owing to the daughter-cells budding 

 again before they have separated from the parent. When the 

 cell is starved, gemmation ceases, fat-globules and vacuoles 



