64 



THE PROTOZOA AS PARASITES OF MAN 



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t Z' 



but if tlu V remain moist until they reach water or human food 

 and are swallowed by a man the cysts germinate in the intestine 



of the new host ; the protoplasm escapes 

 from the cyst as a syncytium with eight 

 nuclei, but the cytoplasm divides so that eight 

 small amoeba are formed. By these the cycle 

 is re-started. 



Entamcvha histolytica, sometimes known as 

 E. dysenteries, also inhabits the human large 

 intestine (Figs. 35, 36). It varies much in size 

 but reaches greater dimensions than E. coli, 

 from which it also differs in being more active 

 (it moves by means of a single large pseudo- 

 podium), in having a distinct ectoplasm over 

 the whole surface of the body, in taking up strongly, while still 

 alive, the stain known as ' neutral red ', and in that the principal 



Fig. 36. — Entamaba 

 histolytica in tlu; 

 encystc<l condition. 

 — After Tantham. 



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@e)5?©?§©9 



Fig. 37. — The life-cycle of Entamoeba histolytica. 



l-n I. Binary fission ; a-/, encystnient and multiple fission. 

 in whirh th.- nucleus has divided ; c. cyst in which the second division has takei 



,,.„,,. , , , ''^"''^'/''■'"^'''V' '•'■■'■*" ^'""'^'^'^''"'^'^'^'"^•^■'th four nuclei which lie close together- 

 /, emiii auiufbul* formed from r by a complicated process of division. logeiner , 



