364 PROTOZOOLOGY 



binary division. Encysted forms have not been observed in this 

 amoeba. 



E. gingivalis is the very first parasitic amoeba that has become 

 known to man. Gros (1849) found it in Russia in the tartar on the 

 surface of the teeth. Some observers maintain that this amoeba is the 

 cause of pyorrhoea alveolaris, but evidence for such an assumption 

 seems to be still tacking. It has been found in the healthy gums and 

 even' in false teeth (Lynch). Therefore, it is generally considered as 

 a commensal. It is widely distributed and of common occurrence. 



In the absence of the encysted stage, it is supposed that the 

 organism is transmitted in trophic forms. According to Koch (1927) 

 who studied the effects of desiccation and temperatures upon the 

 amoeba in culture, the amoeba is killed at 0°C. in 18 hours, at 5°C. 

 in 24 hours, at 10°C. in 48 hours, at 45°C. in 20 minutes, at 50°C. in 

 15 minutes, and at 55°C. in 2 minutes. At 40°C., the survival is said 

 to be for an indefinite length of time. Complete desiccation of the 

 culture medium or immersion in water at 60°C. kills the amoeba. She 

 considered that E. gingivalis may be disseminated both by direct 

 contact and by intermediate contaminated articles. 



E. gedoelsti Hsiung {E. intestinalis (Gedoelst)). In colon and 

 caecum of horse; 6-13/x by 6-1 l/x; endosome eccentric; bacteria- 

 feeder. 



E. equi Fantham. 40-50ju by 23-29/i; nucleus oval; cysts tetra- 

 nucleate, 15-24/i in diameter; seen in the faeces of horse; Fantham 

 reports that the endoplasm contained erythrocytes. 



E. hovis Liebetanz. 5-20m in diameter; in stomach of cattle. 



E. ovis Swellengrebel. Cyst uninucleate; in intestine of sheep. 



E. caprae Fantham. In goat intestine. 



E. polecki (Prowazek). In colon of pigs; 10-12iu in diameter; cyst 

 uninucleate. 



E. dehliecki Nieschulz. 5-10/i in diameter; cyst uninucleate; in the 

 intestine of pig. Hoare (1940) found it in goat also. 



E. venaticum Darling. In colon of dog; similar to E. histolytica; 

 since the dog is experimentally infected with the latter, this amoeba 

 discovered from spontaneous amoebic dysentery cases cf dogs, in 

 one of which were noted abscesses of liver, is probably E. histolytica. 



E. cuniculi Brug. Similar to E. coli in both trophic and encysted 

 stages; in intestine of rabbits. 



E. cobayae Walker (E. caviae Chattcn). Similar to E. coli; in 

 intestine of guinea-pigs. 



E. muris (Grassi). Similar to E. coli; in intestine of rats and mice. 



E. gallinarum Tyzzer. In fowl's intestine; cysts octo nucleate. 



