THE MICROBE OF BREAD 83 



that it takes about 4,000,000 of them to fill the 

 space occupied by a small drop of water. 



Yeast, in its dry form, is alive with the same 

 microbes in their sporadic state, Fig. 57. These 

 spores are about the -$-fa-Q part of an inch in dia- 

 meter. This means that it requires about 32,000,- 

 000 of them to fill the space of the small drop. But 

 they do equally as good work as the microbes of 

 the wet yeast, As soon as the dry yeast is dis- 

 solved in tepid water or milk, and introduced into 

 the dough, the spores increase in size until they 

 are fully grown; then they work exactly as do the 

 microbes of the wet yeast. 



Wet yeast will not keep long. It is .therefore 

 conveniently used in cities and villages, where it 

 can be daily obtained in fresh condition. Dry 

 yeast will keep almost indefinitely. Therefore it 

 is more suitable for use in rural districts, where 

 daily supply is impracticable. 



One may notice that the microbe of bread closely 

 resembles the microbe of beer. There is a natural 

 cause for this. The two originally, in their wild 

 state, are the same. The wild ancestor from which 

 both these microbes have been derived, is thread- 

 like in form, as represented in Fig. 58. By a proc- 

 ess of domestication and culture through many 

 'generations, the brewer has changed the ancestor 

 into the oval form, Fig. 59. By a process of cul- 

 ture along another line, probably for as long a 

 time, the baker has changed the ancestor into the 

 spherical form, Fig. 60. 



