1066 PATHOGENIC PROTOZOA 



repeated binary division of the nucleus. The normal number of 

 nuclei in a coli cyst is eight, yet occasionally cysts are seen in 

 which division has gone on until there are as many as sixteen. In 

 size the cyst measures 10 to 30/x or more. 



Cats or human beings may be parasitized by feeding material 

 containing coli cysts, and in nature, as the cysts are the resistant 

 forms of the parasite, the infection is probably transmitted from 

 one host to another by means of them. No disease, however, results, 

 though the amoebae continue to be present in the stools for years. 



FIG. 129. ENTAMCBBA COLI. Cyst showing eight nuclei. (Arch, fur Protisten- 



kunde, 1912, xxiv.) 



It is possible that fertilization takes place between the young 

 amoebae (gametes?), which are liberated when the cyst dissolves in 

 u new host, as is the case with Entamoeba blattas. 



ENTAMCEBA GINGIVALIS 



(Gros 1849, emend, von Prowazek 1904) 



This amoeba is found in the human mouth both in health and 

 disease. It has been described at different times under various names 

 (bucalis, dentalis) by Gros, Steinberg, von Prowazek, Lewald, Smith 

 and Barrett, Chiavaro and Craig, and quite recently has been sug- 

 gested as the cause of pyorrhea alveolaris by Smith and Barrett and 

 Bass and Johns. It is widely distributed, and has been reported from 

 all quarters of the world. 



The organism is easily found in the tartar at the base of the 

 teeth, in cavities in the teeth, and even at the gum margin in healthy 

 mouths. It varies in size from seven to thirty-five microns, averaging 



