ENDAMCEBA GINGIVALIS AND DISEASE 143 



then there has been much controversy as to the role played by 

 the amebse in connection with the disease, and most authorities 

 are now inclined to look upon the amebse as having little or no 

 important part in the pathogenic process, but this question cannot 

 be considered as settled. The prevalence of amebse in the mouth, 

 even in young children, is well shown by a recent investigation 

 by Anna Williams of the mouths of over 1600 school children in 

 New York City. Of the children between five and seven years 

 of age 35 per cent were found infected, while of those between five 

 and fifteen years 60 per cent were infected. 



The mouth ameba, E. gingivalis, can be found by placing a 

 bit of the pus from a tooth pocket, or the scrapings from the 

 teeth, on a microscope slide. Here the parasites will be found 

 intermingled with pus cells and bacteria. They are from one to 

 three times the diameter of the pus cells, usually from 12 p to 20 ^ 

 (W^TT to TTO <r f an inch) in diameter, and have a granular ap- 

 pearance; the nucleus is relatively very small. Often when 

 stained they show dark bodies inside of them which are probably 

 the nuclei of other organisms or of semi-digested pus cells. When 

 living the amebse prowl about sluggishly, pushing out a blunt 

 pseudopodium now on one side of the body, now on the other, then 

 drawing up the body, and pushing out more pseudopodia, thus 

 slowly working their way about between the pus cells and frag- 

 ments of tissue. The outer layer of the body, or ectoplasm, 

 which serves as a sort of protecting envelope, like the rind on a 

 melon, is clear and transparent but is not readily distinguishable 

 except when the animal is moving. The pseudopodia are always 

 formed first out of this clear ectoplasm, the more granular, gray- 

 ish inner substance or endoplasm pouring out into it later. The 

 reproduction of these little animals is by a simple division of the 

 body into two when they have grown large enough to feel cumber- 

 some as single individuals. Although cysts have been described 

 by some workers, there is insufficient evidence for their existence, 

 and it is more probable that infection is spread by simple direct 

 or indirect transfer of the free amebse from mouth to mouth. 



Some investigators have suggested the possible identity of 

 E. gingivalis and E. histolytica, but, as pointed out by Craig, 

 the sluggish movements, small nucleus, inability to produce 

 dysentery when swallowed and other characteristics all indicate 

 that without doubt the mouth ameba is quite distinct from the 

 intestinal amebae. 



