A MANUAL OF BOTANY 117 



What effect has yeast bread in digestion ? Which are more 

 wholesome, "light" or "unleavened" breads ? What is an 

 enzyme? Why is yeast used in "nonalcoholic'' drinks? 

 What is "root beer"? How do you explain the fact that 

 the yeast plants do not die in a dry yeast cake ? Why are 

 hops often used with yeasts? How may light breads be 

 made without yeast ? 



Type 2. I^acteuia 



General statement. Bacteria are very minute, one-celled 

 fungi (by some placed in another group called Fission fungi), 

 and related in some of their habits to molds and yeasts. 

 They are too minute to be observed by most pupils ; but 

 with proper manipulation of the (Jq)) (400 d.), it is possible, 

 when studying the yeast plant, to observe the very minute 

 dots, dashes, spirals, light or dark tinted, in more or less 

 constant vibration among the yeast cells. The discolored 

 patches on the bread and odor of decay are easily noted. 

 jMany are called germs, and some are frequent cause of 

 serious diseases, not necessarily directly by their presence, 

 but as often indirectly by the poisonous products they pro- 

 duce in their growth (toxins or ptomaines). Cases of poi- 

 soning from ice cream and canned meats are examples. 

 Kead in good reference books about bacteria, and the various 

 means employed to prevent them from injuring foods or 

 attacking the human body. 



Experiments. Try some of the following experiments : — 

 1. Make some meat broth from beef, chicken, or fish ; 

 allow it to cool and then proceed as follows : Take four 

 small bottles, or preferably, test tubes, and number them 

 1, 2, 3, and 4. Into No. 1 i)Our a small quantity of the 

 cooled broth ; do the same with No. 2, but use some cotton 

 for a stopper. For No. 8, boil the bottle and reboil the 

 broth and while both are very hot, pour the broth into the 



1 Bacilli, Micrococci, Spirilli. 



