120 PLANTS WITHOUT CHLOROPHYLL 



causing consumption divides every half hour. Make the following 

 table complete for 24 hours, using numbers only. 



8.30 AM' a bctctcriicnv tctkeiv- irv_^ — 1 



9,00 " tKe •• diTrides — — 2 



9.30 " tKe. tctctericr d-ivide again. — , , =4 



10.00 " «>** '■ ^-=8 



10.30 " -iQ 



11.00 " =32 



11.30 ■• =64 



12.00 M- -128 



12.30P>I- =256 



Conclusion. — 1. How many bacteria would there be in yoiu" 

 lungs at 8.30 a.m. the following morning? 



2. Why do we not catch some disease each day? We breathe, 

 eat, and drink countless dangerous bacteria every day. (See page 

 154, Civic Biology.) 



Problem, 100: What foods are preferreA by bacteria? 



Materials. — Raw meat, cooked meat, white of egg, beans, 

 Indian meal flour, cake, sugar, butter, test tubes, absorbent cotton. 



Method. — Moisten all of the above food substances, place in 

 test tubes with a little water. Expose aU to the air for half an 

 hour. (This can be done during a class period.) Plug with absorb- 

 ent cotton and allow to stand for several days. 



Observations. — Note the appearance and odor of the various 

 substances after five days. 



Conclusion. — 1. In which substances was there rapid growth 

 of bacteria? 



2. Can you make any generalization with reference to the class 

 of nutrients most favorable for the growth of bacteria ? 



Problem, 101: What effect has heat upon the growth of 

 bacteria? 



Materials. — Test tubes, bouillon. 



Method. — Number foiu- tubes containing bouillon. Place 



