2 THE AMERICAN MONTHLY [Jan., 



serve as an introduction to the paper on the spore-form- 

 ing yeasts which was published by the writer* some 

 time ago. % 



The first question is how to obtain the proper material 

 for investigation. Here, a mistake is often made ; the so- 

 called yeast-cakes manufactured and advertised as "man- 

 ufactured of pure yeast " are by no means pure ; every- 

 body who knows a little of pure cultures and mycologi- 

 cal work can see this. The yeast-cakes are very often 

 made of yeast, (but by no means pure), a fair amount of 

 starch, and a fair amount of bacteria is also found. It 

 might be added that there are teachers who let their stu- 

 dents work with this material, and who tell them that 

 the starch-grains visible in the field of the microscope 

 serve as a food for the yeast cells w^iicli break up the 

 grains and form carbon dioxide and alcohol. The only 

 place for obtaining good materials for study is the hreio- 

 ery. 



A 200 c.c. bottle, sterilized, and wrapped in steri- 

 lized filter-paper, is taken to the cellar of the brewery 

 where the fermentation takes place. It is unpacked and. 

 by means of a sterilized string, lowered into one of the 

 vessels. When it is nearly filled, it is drawn up under 

 the surface of the fluid, and corked, before it is taken out 

 in the air. It may be well to take two samples from the 

 same vessel, one a few^ inches under the surface, and one. 

 at the bottom of the vessel. Two clean sticks will facili- 

 tate the latter, one fastened to the bottle, and the other 

 one to the cork. Experience teaches the manipulation. 

 Two such samples should be taken at the beginning, and 

 two at the end of the fermentation. The flasks should 

 be carefully packed and taken to the laboratory. If the 

 preliminary examinations cannot be made at once, the 

 flasks may be kept in an ice box for a few days. 



*The spore-forming species of the genus Snccharomyces. (American Nat- 

 uralist, XXVII, p. 685-696, August 1893). 



