216 HANDBOOK OF PROTOZOOLOGY 



containing varying number of bacteria. The nucleus is observ- 

 able in life. Compared with that of E. histolytica, the endosome 

 is somewhat larger and located ordinarily eccentrically and the 

 peripheral chromatin granules are more conspicuous in the 

 present species. Multiplication by binary fission is known. 

 The precystic stage is similar in appearance to that of the last 

 species with the exception of the nuclear structure, and, there- 

 fore, the differentiation of the two species at this stage is, as a 

 rule, impossible. The cyst resembles also that of E. histolytica, 

 but the mature cyst contains normally eight nuclei and meas- 

 ures 10 to 30 microns in diameter. In young cysts there are 

 glycogen bodies which are larger than those found in E. his- 

 tolytica. The chromatoid bodies are splinter-like and often 

 grouped. This amoeba seems to have been observed first by 

 Lewis in 1870 in India. It is a commensal in the human intes- 

 tine and widely distributed throughout the world. 



Entamoeba gingivalis Gros { = E. huccalis Prowazek) (Fig. 

 85, i-k). The amoeba is a fairly active form. A few blunt 

 pseudopodia are formed and retracted actively. It varies in 

 size from 10 to 40 microns, the majority measuring 10 to 20 

 microns in diameter. The cytoplasm is ordinarily distinctly 

 differentiated ; the ectoplasm is very hyaline and the endoplasm 

 granulated. A single nucleus, numerous food particles which 

 consist of degenerating tissue or pus cells, leucocytes, bacteria, 

 erythrocytes, etc., are found in the endoplasm. The nucleus 

 resembles that of E. histolytica, but the location of the endo- 

 some is inconstant. The amoeba multiplies by binary fission. 

 Cyst is unknown. The transmission of the amoeba from man to 

 man is, therefore, considered direct. 



This amoeba was the first endoparasitic amoeba discovisred 

 and observed by Gros in 1849 in the human tartar. As to the 

 effect of the amoeba upon the host, some investigators believe 

 that it is the probable cause of pyorrhoea alveolaris, but the 

 majority of the investigators are inclined to think that it is a 

 commensal of the human mouth. 



B. Entamoebae of domestic animals 



Almost all domestic animals harbor one or more amoebae 

 in their digestive tracts and many of them resemble those oc- 



