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BACTERIA AND THEIR ROLE IN NATURE 



The telescope revealed to the inhabitants of this globe the 

 vastness of the universe, and the enormous number, the great size 

 and complexity of the planets which compose it. The astronomer 

 spends hours studying this complex aggregate. On the other hand, 

 the microscope has revealed an enormous number of objects which 

 before its time we knew only by the many changes which they 

 produced. We may say that the telescope has revealed the in- 

 finitely large, the microscope the infinitely small. One group 

 of the minute organisms revealed by the microscope we call 

 bacteria. 



What are bacteria? Where do they occur? What are their 

 functions? Are they some of the plagues liberated from Pan- 

 dora's casket to torment the human race? Is it possible that some 

 microbes are beneficial or actually essential to man's welfare? 

 These with many others are the questions which crowd into the 

 mind on hearing the term bacteria. It is the province of this 

 chapter to consider briefly some of these questions. 



What are Bacteria? — To the layman the terms bacteria and 

 microbe usually suggest a minute animal, and we often find them 

 referred to as "bugs." On examinmg them we find that they 

 have many of the characteristics of animals. They are devoid of 

 green coloring matter, chlorophyll, and hence are compelled to 

 live upon complex food as do the animals. Many of them have 

 the power of independent motion. These facts have lent force 

 to the suggestion that bacteria are true animals. Their general 

 form, their methods of growth, their formation of threads and 

 spores, and their similarity in general to some of the lower forms 

 of plant life, green alga^, have caused the biologist to class them 

 as plants. Long before these simple forms of life, bacteria, were 



