222 FAMILY: AMCEBIDM 



under various names by different observers from the material obtained 

 from carious teeth or abscesses in the oral and pharyngeal regions. Smith 

 and Barrett (1915), and in the same year Bass and Johns (1915), studied 

 this amoeba, and concluded that it was probably the cause of pyorrhoea 

 alveolaris, and that it invaded the tissues like E. histolytica. There is no 

 conclusive proof that E. gingivalis is pathogenic in any way or actually 

 invades the tissues, so that it is safer to regard it as a saprophitic organism 

 which lives in the mouth, especially in any pockets which may form in 

 suppurative conditions, along with the numerous spirochsetes, bacteria, 

 and trichomonas. The observation of Lynch (19156) that E. gingivalis 

 may occur in material obtained from the interstices of sets of false teeth 

 worn by individuals with no natural teeth at all and perfectly healthy 

 gums seems difficult to reconcile with the view that the amoeba is, like 

 E. histolytica, a tissue parasite. More recently, under the name of 

 E. macrohyalina, Tibaldi (1920) has described an amoeba obtained from 

 the tonsil. This again is probably no other than E. gingivalis, which has 

 been shown by Smith, Middleton, and Barrett (1914) to invade the crypts 

 of the tonsil under suitable conditions, just as trichomonas and the other 

 organisms of the mouth may do. The bodies which Artault (1898) dis- 

 covered in a cavity of the lung, and which he named Amceha pulmoiialis, 

 are probably the same as those referred to as Entamoeba pulmonalis by 

 Brumpt (1913c). If they are amoebae, which is by no means clear, they 

 may be identical with the oral form. It has been suggested that E. histo- 

 lytica may invade the mouth, and that E. gingivalis is in reality that 

 species. There seems to be no ground whatever for this conclusion, nor 

 is there any reason to suppose that more than one species of amoeba 

 inhabits the mouth. The many names that have been given are the 

 result of observations on degenerate amoebae, just as has occurred in the 

 case of E. histolytica and E. coli. Petzetakis (1923 and 19236) claims 

 to have observed E. histolytica in material coughed up from the lungs in 

 a type of broncho-pneumonia (see p. 193). 



E. gingivalis is a fairly active amoeba when observed on the warm 

 stage, and possesses an ectoplasm which is even clearer than that of 

 E. histolytica. Kofoid and Swezy (1924a) note that sometimes in 

 apparently normal amoebae there is no distinction between ectoplasm and 

 endoplasm. They state that a definite superficial pellicle is always present. 

 As regards its activity, E. gingivalis is perhaps intermediate between 

 E. histolytica and E. coli, and there is a greater tendency to the formation 

 of several pseudopodia at one time. These are smaller in comparison 

 with the size of the amoeba than are those of E. coli and E. histolytica, 

 and according to Jepps (1923a), who has studied the organism in 

 Malaya, they are never formed in the eruptive manner so characteristic 



