HOST-PARASITE RELATIONS: INTESTINAL PROTOZOA 



infect lower animals with Endolimax nana have been 

 made. Kessel (1923) claims to have infected rats by- 

 feeding them cysts. This author (Kessel, 1924) also re- 

 ports positive results with monkeys, but the fact that 

 Brug (1923) found specimens in the monkey indistin- 

 guishable from those of man throw some doubt on these 

 results. Chiang (1925) was unable to infect rats with 

 cysts from man, but found amoebae in the rat similar to 

 E. nana of man which he thinks represents a new species, 

 E. ratti, on physiological grounds. 



3. lODAMCEBA WILLIAMSI 



The so-called "iodine cysts" described by Wenyon in 

 1916 were later found to belong to another harmless 

 commensal, lodamoeha imlliamsi. This species has been 

 found in man in various parts of the world and occurs in 

 about 10 per cent of the general population. Its exact 

 habitat is not known but it probably lives only in the large 

 intestine where it feeds on bacteria. Species of lodamoeha 

 similar to the one in man have been recorded from pigs 

 by O'Connor (1920) and others, and it is possible that 

 the specimens found in man and pig may belong to one 

 species. lodamoeha suis was the scientific name suggested 

 by O'Connor for the pig form. Brug (1921) found an 

 lodamoeha in the feces of a monkey, Macacus cynomol- 

 gus, Hegner and Taliaferro (1924) in another species 

 of monkey, Cebus variegatus, and Wenyon (1926) in a 

 gorilla. Kessel (1923) claims to have infected rats with 

 lodamoeha from man. 



Excystation of lodamoeha williamsi from man in vitro 

 and in guinea-pigs has recently been described by Smith 



124 



