CHAPTER XIV. 

 DISEASES DUE TO PROTOZOA. 



THERE are not many recognized specific diseases in man 

 due to these lowest animal forms, but those well known are 

 of the greatest importance, because of their prevalence in 

 some parts of the world and on account of the difficulties 

 presented to medical treatment. It may be said in general 

 that the protozoan diseases of man represent a phase in the 

 life history of the causative microorganism, and are in fact 

 stages through which the protozoa pass in order to fulfil their 

 cycle of life. The subject of protozoology is of enormous 

 magnitude, and it is impossible even to outline in a work like 

 this all the steps which may be passed through. An attempt 

 will, therefore, be made to describe the important diseases 

 due to protozoa, with a general statement covering the mor- 

 phology and life history of the organism. Of the many 

 thousands of species in nature only a handful are pathogenic 

 for man. The disease-producing types fall into the following 

 zoological families or genera: Sarcodina (rhizopoda, amebse) 

 Mastigophora (flagellata, trypanosoma), Infusoria Hetero- 

 tricha (balantidium), Sporozoa (coccidia, hemosporidia, 

 plasmodium). The diseases, we shall see, all fall into these 

 groups. They are for the most part dependent upon the 

 animal body for the continuance of their life. Other forms 

 live in water, earth, decaying matter, or as apparently harm- 

 less commensal species within the intestinal tract of animals 

 from insects up. 



SARCODINA. 



Amebic Dysentery. Amebic dysentery is a subacute or 

 chronic inflammatory disease of the large intestine, caused 

 by the Entameba histolytica or dysenteric ameba. Contami- 



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