CHAPTER XXXV 



PROTOZOA CAUSING DISEASE— THE GENEEA BABESIA, 

 t^LASMODIUM, ENTAMCEBA, COCCIDIUM AND TRYPANO- 

 SOMA. 



The protozoa are the one-celled organisms belonging to 

 the animal kingdom; they occupy the same general rela- 

 tionship to the higher forms of animals as the bacteria do 

 to the higher forms of plants. They live throughout their 

 lives as single celled individuals or in colonies of single 

 cells. That is to say, the cells do not unite at any time to 

 form tissues or organs and the various species never become 

 multicellular. It was previously noted that there are many 

 intergradations between the bacteria and the protozoa, such 

 as Treponema. 



The protozoa in general, though they are single-celled, 

 are much more complex in structure and in life histories 

 than are the bacteria. The cells of many forms have been 

 greatly modified and different portions of the cell differen- 

 tiated for particular purposes. These specialized parts are 

 termed the organella of the cell. 



Classification of the Protozoa. — All the members of the 

 protozoa may be grouped into two great subdivisions. The 

 first of these includes those forms which can move about 

 either by means of pseudopodia or flagella, the second in- 

 cluding those motile by means of numerous cilia. Cilia 

 differ from flagella in that they are shorter, more numerous, 

 generally blunt, and move the organism about by striking 

 the water in unison, resembling oars in their action. The 

 first subdivision is termed Plasmodroma, the second sub- 

 division CiliopJwra. The group Plasmodroma is divided 

 into three classes: 1. Mastigophora includes those forms 



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