Man's Invisible Friends and Foes 



They were no more cheated to do 

 us harm than were other forms 

 of plant or animal life. If they 

 had their choice they would 

 never enter our bodies at all 



By R. L. Kahn 



WE and the bacteria are 

 close neighbors. Our 

 homes are their homes 

 and wherever we go, they go. 

 But alas! How we misunder- 

 stand their purpose. 



Not long ago, I heard a 

 lecture on these neighbors of ours. The 

 speaker discussed a number of diseases in 

 which bacteria play a part. I do not recall 

 the details, but the impression left I 

 remember well. It was that bacteria are 

 our worst enemies. 



It is well to emphasize the relation of 

 bacteria to disease, but it is important that 

 their relation to health be emphasized also. 

 Their purpose seems to be not to cause 

 disease and death but life and health. 

 Remove bacteria from the world, and life 

 might soon cease. Let them stop work, and 

 plants and animals might starve to death. 



Perhaps no other organisms play a more 

 important role in the evolution of plant and 

 animal life than bacteria. It seems truly 

 inconceivable that organisms so minute 

 should be capable of bringing about such 

 profound changes in every phase of life. 

 Tasks which the greatest chemists cannot 

 perform they carry out with ease. 



What Bacteria Do for the Farmer 



The study of modern agriculture is 

 largely the study of the bacteria of the soil. 

 Decaying organic matter in the soil is 

 transformed into food for plants by bac- 

 teria. Three types of these organisms 

 supply plants with nitrates. One type 

 transforms organic matter into ammonia, 

 another changes the ammonia into nitrites 

 and still another changes the nitrites into 

 nitrates. Such is the division of labor that 

 each kind of bacteria attends to its own 

 specialty. 



One of the products of decay is a gas- 

 sulphuretted hydrogen. The sulphur 

 bacteria decompose this gas and store up 

 free sulphur in their own bodies. But the 



supply of sulphuretted hydrogen is soon ex- 

 hausted. The bacteria perish and free 

 sulphur is liberated. Ultimately we get 

 sulphate of lime, an important constituent 

 of plant food. There are also bacteria 

 which supply plants with iron, and count- 

 less others which help in one way or another 

 to make plant life possible. 



If it were not for bacteria, the world 

 might be piled up with dead plants and 

 animals. Bacteria are the scavengers of 

 the living world. As soon as the life of an 

 animal or plant ends, bacteria gather 

 around it, take the body apart, and reduce 

 it to the elements of which it was 

 originally built. 



This inherent power makes bacteria per- 

 petuators of life. Matter, we know, is 

 indestructible. The elements which go to 

 build up an animal or plant are not in any 

 way affected when the animal or plant 

 dies. Let these elements be set free, and 

 Nature will utilize them for the construction 

 of other living bodies. To bacteria it is 

 given to supply Nature continually with 

 elements so that she may always build new 

 living structures. 



Are Bacteria Necessary to Health? 



Whether or not health is possible with- 

 out bacteria is to-day one of the most 

 interesting problems in the field of biological 

 science. The question is far from settled. 

 Nuttal and Thierfelder, two well-known 

 scientists, believe that it is possible for 

 animals to live and retain their health with 

 sterilized air, food and water. Some 

 famous experiments carried out by Cohendy 

 and Wollman at the Pasteur Institute, 

 Paris, also seem to indicate that animals 



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