584 



A MANUAL OF BACTERIOLOGY 



the ordinary pyogenic organisms are absent, unless a 

 secondary infection has occurred, which is the exception. 

 The abscess is usually single, and Rogers suggests that 

 the amoebae reach the liver through adhesions between it 

 and the bowel. 



The presence of the amoebae and their cysts in the 

 faeces forms a valuable diagnostic feature of amoebic 

 dysentery. The E. histolytica has to be distinguished 

 from another form, E. coli (see below), which is common 

 in the intestine. In the amoebic stage, the presence of 

 red corpuscles in E. histolytica and of bacteria in E. coli 

 are the chief distinguishing features. In the cystic stage, 

 the cyst of E. histolytica is characterised by never having 

 more than four nuclei, while that of E. coli has up to 

 eight, or even more, nuclei. The following table gives 

 the principal differential characters of the two forms : 



E. coli. E. histolytica. 



15-30 p.. Histolytica form, 15-30 p. 



Minuta form, 10-20 p.. 

 Clear differentiation into 

 ectoplasm and endo- 

 plasm. Frequently 



encloses red blood cor- 

 puscles. 



Smaller, spherical, with 

 finely granular mem- 

 brane. Indistinctly 

 seen. 



More refractile. 

 Fairly actively amoeboid. 



Size 



Cytoplasm 



Nucleus 



Kefractility 

 Amoeboid 



movement 

 Cysts . . 



No differentiation into 

 ectoplasm and endo- 

 plasm. Never en- 

 closes red blood cor- 

 puscles. 



Large, spherical, with 

 coarsely granular 

 membrane. Clearly 

 visible. 



Less refractile. 



Sluggishly amoeboid. 



. Accurately spherical, 

 15-20 p., less refrac- 

 tile. Contains more 

 than four, and up to 

 eight, nuclei. 



Entamceba coli is a common inhabitant of the large 



Not so accurately 

 spherical, 10-14 p., 

 more refractile. Two 

 to four nuclei present. 



