8 Biological Relation Between Bacteria and the More 



The energy which is stored in the complex chemical com- 

 binations of the plants of higher organization with the 

 aid of their chlorophyl and sunlight is used by the animal 

 organisms for the production of animal heat and the 

 different functions of the body. 



With this very brief consideration of the general biologi- 

 cal functions of the bacteria and the more highly organized 

 flora, we are in a position to consider briefly the relation 

 which these organisms bear to each other in running 

 streams. This relation has been studied to some extent 

 by experimenters with the view of discovering something 

 about the modus operandi of the self-purification of pol- 

 luted streams. It has been found that the chlorophyl- 

 bearing organisms are confined largely to fresh, running 

 water. These organisms do not multiply very rapidly, 

 and may even die off, in polluted waters. The conditions 

 for growth in waters of this character are not very favor- 

 able for these organisms. The greater the degree of pol- 

 lution the more the action of sunlight the most essential 

 feature of the life and growth of chlorophyl-bearing plants 

 is interfered with in these waters. The character of the 

 food material is not adapted to their growth because of the 

 predominance of organic substances in the water. Besides 

 this, because of the presence of large quantities of organic 

 matter, we have immense numbers and different kinds of 

 chlorophyl-free organisms in water of this character, and 

 these are doubtless in a certain degree antagonistic to the 

 chlorophyl-bearing organisms : so that their growth is 

 interfered with in this manner. 



As has been said, the large quantity of organic matter 

 in polluted water, the hindrance of the action of sunlight, 

 and the presence of suspended matters, makes this a favor- 

 able soil for the growth and multiplication of all chlorophyl- 

 free organisms. They find here an abundant food supply 

 and abundance of oxygen, and all other conditions favor- 

 able for growth. In the studies which have been made 



