HABITAT OF YEASTS 107 



found in the salt waters of the sea (Fischer and Brebeck ). 1 They 

 are frequently encountered in milk. (Maze, Dombrowski.) Finally 

 many of the Mycoderma live in alcoholic beverages. 



Many of the yeasts live as parasites in man and animals and cause 

 quite varied lesions. 



Duration of Life of Yeasts 



The yeasts are capable of conserving themselves for a long time in 

 the same media without perishing. Duclaux, 2 who has given this 

 subject some attention, had the privilege of studying some of the cul- 

 tures which Pasteur had used in his investigations on alcoholic fer- 

 mentation. In 1885, after 5 or 6. years, in 15 attempts on old yeasts, 

 he found only three which had died out. In 1889, after 11 to 17 

 years, out of 26 yeasts only 6 could not be revived. He has been able 

 to observe living yeasts after 25 years. From this it will be seen 

 that the yeasts are able to live for a long time in media in which the 

 ordinary foods have been exhausted and to use materials which or- 

 dinarily would not be taken. Hansen found that yeasts could be kept 

 for periods of from 13 to 17 years in a liquid containing 10 per cent 

 of sucrose without acid. 



Recent observations by Klocker 3 at the laboratory in Carlsberg 

 have shown that living cells of yeast were present in sucrose and beer 

 wort solutions after 20 and 30 years. Will 4 has also found that yeasts 

 would live for a long time in media such as beer wort. Among the 

 cultures which were examined, the oldest was 18 years and 2 months. 



Will 5 has published data on the longevity of yeasts under different 

 conditions. He found that the yeasts would live longer in liquid gela- 

 tin because these remained moist longer. Even in dry cultures there 

 would be living cells after a long time. Meissner 6 secured some 



1 Brebeck, B. and Fischer, B. Zur morph. Biol. und Syst. d. Kahmpilze, 

 Jena, 1891. 



2 Duclaux, E. Traite de Microbiologie, Fermentation alcoolique 3, Paris, 

 1900. 



3 Klocker, A. Fermentation organisms. III. Conservation of fermentation 

 organisms in different nutritive media. Comp. Rend. trav. lab. Carlsberg, 11 

 (1917), 297-311. 



4 Will, H. Noch einige Mitteilungen iiber das Vorkommen von lebens- und 

 vermehrungsfahigen Zellen in alten Kulturen von Sprosspilzen. Cent. Bakt. 48 

 (1917), 35-41. 



6 Will, H. The persistence of living yeast on gelatin cultures. Cent. Bakt. 

 Abt. II, 31, 436-453; Beobachtungen liber das Vorkommen lebens- und vermeh- 

 rungsfahigen Zellen in sehr alten Wiirzkulturen. Cent. Bakt. Abt. II, 44, 1916, 

 58-75. 



6 Meissner, R. Ten-year experiment on the longevity of wine yeasts in pure 

 cultures on 10 per cent cane sugar solutions. Zeit. Garungsphysiologie, 1, 106-113. 



