FERMENTATION 239 



Examine some of the mixture under the micro- 

 scope. Note the multitude of globular or slightly 

 ovoid bodies, the largest about T ^^ mm. in diame- 

 ter. They are motionless. Many have put forth 

 buds. They seem to be plants in active growth. 1 



1. Place 300 c.c. of the nutrient liquid (Ex- 

 periment 1) in a flask holding 500 c.c. Add a 

 piece of fresh compressed yeast the size of a pea. 

 Place the flask in a temperature of 35 C. 



Note that as fermentation advances the yeast 

 increases in quantity. 



2. Place a small piece of fresh compressed 

 yeast in a test-tube. Fill the tube with nutrient 

 liquid and invert it in a dish of similar liquid. The 

 tube may be kept upright by a clamp. Let the 

 mixture stand twenty -four hours in a warm room. 



with the salts present in the ash of yeast (Pasteur). A useful 

 substitute is 



Potassium phosphate ... 20 gms. 



Calcium phosphate ... 2 



Magnesium sulphate ... 2 



Ammonium tartrate . . . 100 



Cane sugar 1,500 



Water 8,376 



10,000 



(Practical biology, Huxley and Martin. ) 

 1 Cagniard-Latour : L'lnstitut, 1835, iii, p. 150 ; also Annales 

 de chimie et de physique, 1838, Ixviii, p. 206. The yeast plant 

 was first observed microscopically in beer-yeast by Leeuwen- 

 hoek, 1680, but he did not associate fermentation with the 

 growth of the yeast. 



