PROTOZOA IN THE DIGESTIVE TRACT 45 



Keys to the genera and species of flagellates living in 

 the digestive tract 



A. The trophozoites in fresh and stained smears 



1(2) In the tartar of teeth Trichomomis elongata (p. 41) 



2(1) In dysenterie or diarrhoeic faeces 3 



3(4) The trophozoite l^ilaterallv symmetrical; witli two nuclei; 



eight flagella Giardia intcstinaJis (p. 41-44) 



4(3) The trophozoite not bilaterally symmetrical 5 



5(6) Witli an unduhiting membrane and axostyle 



Trichomonas hominis (p. 38-41) 



6(5) Without undulating membrane 7 



7(10) With a cytostome near the anterior end 8 



8(9) With a large cytostome in which a short flagellum occurs; 



3 anterior flagella; body 10-15|x long. .Chilomastix mesnili (p. 36) 

 9(8) With a small cytostome; two flagella; body 4-9|ii long. . . . 



Retortamomis intestinalis (p. 31-33) 



10(7) Without a visible cytostome 11 



11(12) Body more or less rounded; 3 anterior flagella; body about 



4-6!lI in diameter Enteromonas hominis (p. 34-35) 



12(11) Body more or less pyriform; 3 anterior flagella and one pos- 

 terior flagellum; body about 4-101.1 long 



Tricercomonas intestinalis (p. 35-36) 



B. The cysts in fresh and stained smears 



Enteromonas hominis, Trichomonas hominis, and T. ehmgata ha\e not 

 been seen in encysted condition 



1(4) Cysts pyriform 2 



2(3) Cysts small, 4-5-7|ii ^^^iig Retortamonas intestinalis (p. 31) 



3(2) Cysts large, 7-10^1 long Chilomastix mesnili (p. 36) 



4(1) Cvsts ovoid with nearly equally rounded ends 5 



5(6) Cysts 6-8ti by 4-6!.i; 1, 2, or 4 nuclei 



Tricercomonas intestinalis (p. 35) 



6(5) Cysts 8-14|Li by 6-10ii; 2 or 4 nuclei; with se\'eral fibrils 



Giardia intestinalis (p. 41) 



