546 Protozoa of the Digestive and Urogenital Tracts 



duces forms with projecting axostyles and disproportionately long mem- 

 branes (71). Mitosis has been described by Hinshaw (71), and T. tenax 

 has been compared with other trichomonads of man by Wenrich (175). 

 Although rarely present in the healthy mouth, infection with T. tenax 

 may approach an incidence of 90 per cent in cases of advanced pyorrhea 

 (13, 72, 76). However, a casual relationship to pyorrhea has not been 

 established (95, 97). In addition to their occurrence in the mouth, the 

 flagellates have been found occasionally in pus from infected tonsils and, 

 rarely, in material from the lungs. 



Entamoeba gingivalis 



This species, described as Amoeba gingivalis by Gros in 1849, 

 evidently was the first amoeba reported from man. The specific name, 

 Endamoeba buccaUs, was proposed later by Prowazek (133) who had over- 

 looked the paper by Gros. Several detailed descriptions have been 

 published more recently (30, 78, 99, 104), and mitosis has been described 

 by Stabler (155a) and Noble (128a). Literature on the species has been 

 reviewed by Kofoid (95). 



The amoeba measures 6-60[x in length, usually shows clear pseudo- 

 podia, and may contain a number of food vacuoles containing leucocytes, 

 or less commonly, bacteria (Fig. 11. 1, D-F). The amoebae ingest living 

 leucocytes and consequently are not mere scavengers (30). In cultures, 

 both leucocytes and red corpuscles are ingested (78). The nucleus, 2-6[jl 

 in diameter, often shows a central clump of granules, as well as a zone 

 of coarse granules near the nuclear membrane. 



The incidence of infection apparently increases with age, although 

 the healthy mouth rarely harbors E. gingivalis. In cases of pyorrhea, the 

 incidence is high and may exceed 90 per cent (72). Such a coincidence is 

 tempting but there is no conclusive proof of pathogenicity (97). This 

 amoeba seems to be a natural parasite of monkeys (68, 90, 99) as well 

 as of man, and experimental infections are possible in dogs with a pre- 

 existing gingivitis (74). 



FLAGELLATES OF THE 

 HUMAN INTESTINE 



The small intestine is invaded only by Giardia lamblia, whereas 



the colon may contain Retortomonas intestinalis, Tricercomonas intesti- 



nalis, Cliilomastix mesnili and Pentatrichomonas ho7ninis. 



Retortomonas intestinalis 



(Wenyon and O'Connor) Wenrich 



This flagellate, often known as Embadomonas intestinalis (Wen- 

 yon and O'Connor) Chalmers and Pekkola, has been reassigned to Re- 

 tortomonas by Wenrich (165) on the basis that Embadomonas Mackin- 



