Respiration, Digestion, and Fermentation. 105 



position of the storage substances in the various seeds 

 tested ? 



109. Products of fermentation — Make up 1,000 cc. 

 of a 10 per cent, solution of cane sugar, and add to it a pack- 

 age of compressed yeast, or make a Pasteur's solution by add- 

 ing to 838 cc. distilled water, 10 cc. ammonium tartrate, 

 150 cc. saturated solution of grape sugar, and 2 grams 

 each of magnesium sulphate, calcium phosphate, and po- 

 tassium phosphate. After the ingredients are thoroughly 

 mixed, fill a tall glass cylinder about one-third full, and 

 cover tightly. Introduce a package of compressed yeast. 

 Test the air above the solution for carbon dioxide, as in 

 §104, a few hours later. Taste the solution. The sugar 

 originally present is split up by the action of an enzyme 

 secreted by the yeast cells into carbon dioxide, water, and 

 alcohol. 



no. Influence of various factors on fermentation. 

 — Repeat the test given in the previous experiment, but 

 introduce a few cubic centimeters of chloroform into the 

 solution. Note effect. Repeat the test again, but set the 

 cylinder containing the solution and yeast in a larger vessel 

 containing water. Add large pieces of ice to the water, and 

 renew. Take temperature of water occasionally. What effect 

 does the low temperature have upon the fermentative action ? 

 What is the action of yeast in the rising of dough in bread- 

 making ? 



III. Action of diastase and associated enzymes. 

 — Place 10 grams of seeds of barley in a germinator for 

 thirty-six hours, or until the radicles are about 5 mm. in length. 

 Grind fine in a mortar or in a new coffee mill. Collect the 

 mass in a clean glass vessel, and add 30 cc. distilled water, 

 and stir. A half hour later filter, receiving the filtrate in a 

 large test tube or small bottle. Make a starch paste by 

 adding i gram starch to 100 cc. water, which should give 



