'24'2 CEKGOMONAS INTESTINALIS. 



stances which make the existence of these parasites possible. But as 

 such admixtures are more frequently found in the urine of animals 

 (as Leeuwenhoek has shown in the case of the horse), the presence of 

 these creatures is by no means rare in fresli urine. 



Of all the parasitic forms described as occurring in man, there is 

 only one which we know with tolerable accuracy Cercomonas in- 

 testinalis. It is by no means identical, however, with Trichomonas 

 (Fig. 119) and Hexamita (Fig. 120), mentioned by Ehrenberg and 

 Dujardin as belonging to the same species, and already referred to 

 as living in the cloaca of frogs and newts. Further, all the human 

 parasites found in diarrhcetic stools, and described as Cerconwnas in- 

 testinalis, do not, as we shall afterwards see, really belong to this 

 species. 



Cercomonas intestinalis, LambL 



Davaine, Comptes rendus Soc. biolog., 1854, " Traite* des Entozoaires Synops.," ed. 2, 

 p. xxiii.. 1854 (Cercomonas hominis). 



Ekeckrantz, "Bidrag till kannedomen om de i menniskans tarmkanal fb'rekommande 

 Infusorier," Nordisk med. Arkiv, Bd. i., No. 20 (Virchow-Hirsch, Jahresber., Bd. i., p. 

 202, 1869). 



Tham, "Tvanna fall af Cercomonas," Upsala Idkare Foren. Forhandl., Bd. v., p. 691 

 (VircJiow-Hirsch, Jahretber., Bd. i., p. 314, 1870). 



Lambl, " Cercomonas et Echinococcus in hepate hominis," Rutsian Medical Report, 

 No. 33, 1875 (Russian). 



Zunker, " Ueber das Vorkommen der Cercomonas intestinalis im Digestionskanal des 

 Menschen und deren Beziehung zu Diarrhoen," DeutscJie Zcitschr. filr praktiscJie Medici*, 

 No. 1, 1878 (proparte). 



[Grassi, " Intorno ad alcuni protisti endoparassitici," Atti. Soc. Ital. sci. not., vol. 

 xxiv., pp. 12-22, 1882. R. L.] 



The body is generally pear-shaped, and bears a rigid terminal fila- 

 ment almost as long as itself, in addition to the much longer and very 

 delicate vibrating u'hip-shaped flagellum. 



As I have already said, Cercomonas intestinalis is known " with 

 tolerable accuracy," and this is due to the descriptions of Davaine, 

 whose observations, although the oldest on the subject, are still the 



FIG. 121. Cercomonas intestinalis. A, larger, and B, smaller variety. 

 (After Davaine. ) 



most exact and best we possess (Fig. 121). Yet even Davaine distin- 

 guishes two varieties of these forms, differing from each other in form 



