LINDNER'S CONCAVE-SLIDE METHOD 83 



EXERCISE 25. LINDNER'S CONCAVE-SLIDE METHOD 

 FOR DEMONSTRATING FERMENTATION 



The object of this exercise is to test the fermenting 

 power of yeasts. 



Apparatus. Three clean concave slides; three clean 

 cover-glasses; sterile filter paper (place several pieces 8 cm. 

 square in a Petri dish and sterilize in the hot air); three 

 tubes of sterile wort or cider; three sterile 1 c.c. pipettes; 

 forceps; melted paraffin; platinum needles; Bunsen burner. 



Cultures. Saccharomyces cerevisice; Saccharomyces apicu- 

 latus; Torula rosea. 



Method. The following procedure is to be used for each 

 organism to be tested: 



1. Using the straight needle, inoculate a tube of wort 

 with Saccharomyces cerevisioe and mix well through the 

 medium. 



2. Sterilize a concave slide in the flame. 



3. Using a sterile pipette, fill the concavity of the 

 slide until the liquid " rounds up " over the concavity. 



4. Holding a cover-glass in the forceps, sterilize it in 

 the flame. 



5. Lay the cover-glass on the end of the slide and push 

 it over with the forceps until the cover-glass covers the 

 concavity, thus sealing in the inoculated liquid. There must 

 be no air bubbles. The preparation must be made over again 

 if this occurs. 



6. Remove the excess liquid with sterile filter paper, 

 using forceps to hold the paper. 



7. Seal the cover-glass with paraffin as with the adhesion 

 culture. 



8. Place the slides in a horizontal position in Petri 

 dishes, or in a slide box as convenient. 



9. Incubate at 25 to 30 for twenty-four hours. Gas 

 bubbles will be formed in twenty-four to forty-eight hours, 

 if any fermentation occurs. 



