282 BACTERIOLOGY FOR NURSES 



found that as the amebse multiplied they traveled toward the 

 edge, and in passing the rings of bacteria they deposited the living 

 organisms with which they started and took up the dead ones. 

 Thus after forty-eight to seventy-two hours active amebse free 

 from living bacteria were found at the periphery. It has recently 

 been found that certain strains of intestinal amebse will grow in 

 pure culture when inoculated on sterile tissue such as brain, liver, 

 or kidney placed in nutrient agar. 



E. Coli. Various investigators have reported the presence 

 of E. coli in from 20 to 60 per cent of all normal stools examined 

 regardless of locality. The organisms vary from 20 to 40 /* in 

 diameter. As a rule they are less actively motile than E. histolyt- 

 ica and contain more and larger vacuoles, which usually are filled 

 with bacteria and rarely with the red blood cells so palatable to 

 the latter. Another distinguishing characteristic is their division 

 in the encysted form. E. histolytica usually produces only four 

 daughter cells, while the normal number for E. coli is eight. Ex- 

 periments have demonstrated that parasitism may be brought 

 about by feeding human beings with E. coli cysts. No disease, 

 however, results, though the amebse may be present in the intes- 

 tines for years. 



Entameba Gingivalis. The organism is almost invariably 

 present in pyorrhea alveolaris, but it is also present in normal 

 mouths, and as yet no experimental evidence has established its 

 relation to the disease. The organism can readily be found in 

 tartar scraped from the teeth near the gum margin. It measures 

 from 12 to 20 /* in diameter, contains a nucleus and many food 

 vacuoles. Multiplication occurs only in the vegetative stage and 

 then by simple division. Cyst formation does occur, but it is 

 purely a protective stage and not one of reproduction. 



FLAGELLATA 



The flagellata, as their name implies, are characterized by the 

 possession of one or more flagella. They are divided into several 

 subclasses. Those pathogenic to man belong chiefly to the genera 

 Trypanosoma and Leishmania. 



