Chapter 2 

 Protozoa parasitic in the digestive tract 



THERE are fifteen species of protozoa which have been 

 reported to inhabit the digestive tract of man. Of these 

 six belong to Sarcodina, seven to Flagellata, and one each 

 to Sporozoa and Cihata. 



Sarcodina 



The amoebae which inhabit the human body all belong 

 to the group Amoebina, and are parasites of the digestive 

 system. The tiophozoites absorb fluid nourishment and 

 also engulf solid food particles. They multiply by binary 

 fission. If the trophozoites leave by accident the human 

 intestine, they perish within a short period of time. En- 

 cystment takes place in four species. The cysts are capable 

 of remaining alive outside the host body in the faeces, 

 water, etc., for a considerable length of time and become 

 the source of infection. When they are taken into the 

 human mouth in contaminated water or food, the cysts 

 pass through the stomach unharmed and excyst in the 

 intestine. The emerged amoebae, if not uninucleate, divide 

 to form uninucleate individuals and develop into tropho- 

 zoites. 



The first three amoebae described in the following 

 pages, have been in recent years designated by several 

 writers as Endamoeba apparently in accordance with the 

 opinion expressed by no. 99 of the International Commis- 

 sion on Zoological Nomenclature ( 1928). This manual does 



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