CHAPTER II 



BACTERIA AND PROTOZOA 



BACTERIA 



J]N the border line between the plant and 

 the animal worlds are many forms which 

 possess some of the characteristics of 

 _ _ Yx>th. Indeed when an attempt is made 

 to separate all known organisms into two groups 

 one is immediately confronted with difficulties. In 

 looking over the text-books of Botany we will find 

 that certain low forms are discussed there as belong- 

 ing with the plants, and on turning to the manuals 

 of Zoology we will find that the same organisms are 

 placed among the lowest forms of animals. The 

 question is of course of little actual importance 

 from certain points of view. It serves, however, to 

 show the close relation of all forms of life, and from 

 a medical standpoint it may be of very great im- 

 portance owing to the difference in the life-habits, 

 methods of reproduction and methods of trans- 

 mission of many of the forms that cause disease. 

 We have already seen that none of the diseases that 



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