1894.] MICROSCOPICAL JOURNAL. 35 



THE PURE CULTURE. 



Pure cultures of yeasts beg-in with a microscopical ex- 

 amination of the sample in order that the results maybe 

 somewhat estimated. We shall again illustrate by an 

 example. 



The microscopical picture of a yeast sample is demon- 

 strated by Fig. 1. Three forms of cells are found, (a) 

 round and oval, isolated culture-yeast cells, (b) round 

 and oval cells in small rows, (c) pastorian cells, isolated 

 or in rows. 



A few drops from the yeast flask are deposited in a 

 Chamberland or Freudenreich flask half filled with ster- 

 ilized water. This is shaked violently for a couple of 

 minutes, and the contents have then a milk-and-water 

 like appearance. From this flask a drop is again trans- 

 ferred into sterile water, stirred, and from this second 

 flask a third and similar transfer is made. These water 

 flasks are previously marked and numbered. The two 

 last flasks remain in the culture box ; the whole process 

 should be carried out here. The water in the last flask 

 contains a number of cells pr. cc. very insignificant when 

 compared with the original emulsion. If a drop from 

 this is examined microscopically, only one or two cells 

 must be observed within the field of the microscope. If 

 there are more, another transfer is made, a suitable 

 amount of the emulsion in flask No. 3 being transferred 

 in order to make sure the result. When the transfer has 

 been made, the flasks should always be stirred. 



While this takes place, a 10 per cent beer-wort gelatine 

 is ready for use in a water bath by 40''C. which tempa- 

 ture keeps it liquified. When ready for use it is cooled 

 down to 30°C. and taken into the Hansen box where the 

 following apparatus is waiting : 



1. The yeast emulsion containing the proper amount of 

 cells. 



2. A big moist chamber. (See Fig. 2). 



