224 



THE PROTOZOA 



a parasite of a dangerous kind, which occurs in tropical and subtropical 

 regions, and is the pathogenic agent of amoebic dysentery and liver-abscess ; 

 it attacks and devours the tissues of the host, destroying the wall of the 

 intestine, whence it penetrates into the blood-vessels and is carried to the 

 liver, where it establishes itself and gives rise to liver-abscesses. These two 

 species of amoebae are distinguishable by structural characters. E. coli has 

 a relatively fluid body, with ectoplasm feebly developed and with a fairly 

 large spherical nucleus (or nuclei) lodged in the endoplasm. E. histolytica, 



FIG. 89. Entamceba coli. A and B, Living amoebae showing changes of form and 

 vacuolation in the endoplasm ; 0, D, E, amoebae showing different conditions 

 of the nucleus (n.) ; F, a specimen with two nuclei preparing for fission ; 

 G, a specimen with eight nuclei preparing for multiple fission ; H, an encysted 

 amoeba containing eight nuclei ; /, a cyst from which young amoebae 

 (al) are escaping ; J, K, young amoebae free. After Casagrandi and 

 Barbagallo. 



on the contrary, has a relatively viscid body with greatly-developed ecto- 

 plasm, as is seen clearly in the formation of pseudopodia, which may consist 

 entirely of ectoplasm ; it is smaller than E. coli, and its nucleus has a com- 

 pressed form, stains feebly, and is lodged in, or immediately below, the 

 superficial ectoplasmic layer. The life-cycles of these two species are also 

 very different, as described by Schaudinn. 

 E. coli, in the amoeboid multiplicative phase, reproduces itself by binary 



