566 A MANUAL OF BACTERIOLOGY 



the blood acquires specific agglutinative properties, agglutinating 

 the yeast -cells of the species with which the inoculation has been 

 carried out. 1 



On the yeasts of fermentation, see Jorgensen, Micro-organisms 

 and Fermentation, 4th ed., 1911 (C. Griffin & Co.), (full bibliog.) ; 

 Klocker, Fermentation Organisms. 



Examination of Yeasts 



The yeasts can be readily examined in the fresh state in hanging - 

 drop preparations. The cells should be young or they will not be 

 of the typical form ; a two or three days old culture in wort 

 or grape-sugar solution may be used. The yeasts grow well at 

 20-30 C. on the ordinary gelatin, agar, and potato, but wort 

 gelatin or wort agar is to be preferred. The elongated cells, 

 common to all old cultures of yeasts, may be obtained from the 

 films which form on wort cultures in wide flasks or beakers after 

 two or three weeks. 



In order to stain yeasts, a dilution of the culture should be 

 made in a watch-glass of water, so that the cells may be isolated, 

 as they become distorted if grouped in masses. 



If the yeast has been grown in wort, it is best, before staining, 

 to pour off the fluid from the deposit of cells at the bottom of the 

 flask or test tube, add some physiological salt solution and shake, 

 then allow the vessel to stand for an hour for the cells to sediment, 

 or centrifuge, and the process of washing may be repeated once. 

 Films may be prepared in the ordinary way and stained for five 

 minutes in Loffler's methylene blue, washed in water, dried, and 

 mounted. Or the films, after air-drying, may be fixed by immer- 

 sion in equal parts of alcohol and ether for ten minutes, dried in 

 the air, and stained as before. The preparations can also be 

 stained in gentian violet or fuchsin, or by Gram's method. 



Ascospores may be double stained by preparing films of a 

 sporing culture in the ordinary way, staining with carbol-fuchsin 

 for two minutes, rinsing in water, decolorising with 5 per cent, 

 sulphuric acid and with alcohol, rinsing in water, counter- staining 

 with Loffler's blue for five minutes, washing, drying, and mounting. 

 The spores are red, the remainder of the cells blue. 



See Macfadyen, Centr. f. BaTct. (1* Abt.), xxx, 1901, p. 368. 



