72 



THE STRUGGLE FOR EXISTENCE 



them as a source of energy. Sugar is almost entirely utilized to 

 obtain the available energy, and serves as food only in a very slight 

 degree. As a result a considerable amount of alcohol accumulates in 

 the nutritive medium, which corresponds pretty well to the amount 

 of sugar consumed. Curves of such an accumulation of alcohol, 



16 - 



>» 



V. 10 



o 



■w 8 



c 



o b 



First experiment 



16- 



*/2 



curve 



Growth curve 



30 io 

 Hours 



so 



60 



Second experiment 



/ 



_ — <s Alcohol curve 



Growth curve 



16 



H 



*,* 



06-% 

 02 



70 



IS 



2 0^ 



o 



-10 



-OS 



50 



60 



10 



30 VO 



Hours 



Fig. 11. The growth in volume and accumulation of alcohol in Saccharo- 

 myces cerevisiae in test tubes. From Gause ('32b). 



taken from the paper of Gause ('32b), are represented in Figure 11. 

 Here are given the results of two experiments made in test tubes, but 

 on a nutritive medium of somewhat different concentration. In both 

 cases a certain time after the experiment was begun the accumulation 

 of alcohol (and, consequently, the consumption of sugar) proceeds 



