164 



METHODS OF CULTURE AND ISOLATION 



If one wishes to use volumetric methods, an apparatus must be ar- 

 ranged which will collect all of the gas as it is formed during the fer- 

 -^ mentation. Such an apparatus was arranged by Slator. 1 



t An ordinary nitrometer will be sufficient and should be 



filled with mercury to prevent absorption of the gases, 

 which would occur if water or other liquids were used. 

 Euler and Lindner 2 have described the Meissl ventila- 

 tion valve (see Fig. 69-B) which may be used to allow 

 the carbon dioxide which is formed during fermentation 

 to escape but which retains the water. A small amount 

 of concentrated sulfunc acid is put into the valve to act 



as an absorbent to retain moisture. The formation of 



Fig 69-B carbon dioxide may be followed by the loss in weight at 



Meissl Ven- various intervals. These losses in weight may be plotted 

 for* Determin- according to the time at which they occurred in such a 

 ing the Fer- way that the curves may be made which express the 

 ment of g Ye\ b st8 fermenting ability of each 



ity 



(Euler -Lind- 

 ner). 



yeast. By means of these, 



one is able to compare 

 the yeasts under examination quickly and 

 to determine which is the most "effi- 

 cient." Alwood 3 has devised a similar 

 valve which is used in the same manner 

 as the Meissl valve. (See Fig. 69-C.) 

 Other devices may be resorted to for 

 reaching the same end. 



Preservation of Yeasts: It is often 

 advantageous to keep yeasts over a long 

 period of time without having to transfer 

 them to fresh media very often. Such is 

 the case with laboratory collections. 

 Then, again, it is often desirable to 



exchange cultures between laboratories Fig. 69-C. Detail of Alwood 

 and in many cases the distance is great 

 and months are required to cover it. 

 of preserving the yeasts which have been collected in the countries 

 which they visited. According to the investigations of Hansen, 4 



1 Slator, A. Jour. Chem. Soc. 89 (1906), 128. 



2 Euler, H., and Lindner, P. Chemie der Hefe unter der alkoholischen Garung. 

 Leipzig, 1915. 



3 Alwood, W. B. The fermenting power of pure yeast and some associated 

 fungi. U. S. Dept. Agriculture, Bureau of Chemistry, 111-1908. 



4 Hansen, E. C. Recherches sur la physiologic des ferments alcooliques. 

 Comp. Rend, du lab, de Carlsberg, 13, 1898. 



Fermentation Valve. 

 Explorers have had need 



