The students at each bench should make a combined table 

 of their results as to gas-formation, change in opacity, and 

 change in number of torulse, using + and - as signs. 



(B) ON FLUID. (a) Disappearance of Sugar. (Demon- 

 stration.) The original solution (A) and the solution after 

 incubation (B) have been boiled for some time with phenyl- 

 hydrazine and acetic acid, which forms a yellow insoluble 

 compound with glucose. Note the difference in the amounts 

 in (A) and (B). 



(6) Formation of Alcohol. Some of the fluid from tubes 1, 

 after being in the incubator, is distilled. To about half an inch 

 of the distillate, add a few drops of potassium bichromate 

 and a little dilute sulphuric acid and warm. Note : 



1. Pungent odour Aldehyde. 



2. Green colour. 



(c) Nature of Gas evolved. (Demonstration.) With a fine 

 pipette add KHO dissolved in alcohol to a Doremus' ureameter 

 in which the solution has been incubated with yeast, and note 

 the absorption of the gas evolved C0 2 . 



4. CONCLUSIONS. (1) What has happened to the yeast in 

 each of the tub'es ? 



(2) What conclusions do you come to as to the influence 

 upon the yeast protoplasm of the various conditions to which 

 it has been subjected ? 



(3) How has the growth of the yeast taken place ? 



(a) Where does yeast protoplasm get material for 



growth ? 

 (6) Where does yeast protoplasm get energy for growth ? x 



1 For Enzyme Action see Practical Chemical Physiology, by Noel 

 Paton, Cathcart and Burns (Fourth Edition), p. 23 et aeq. 



