PART II. CHARACTERS AND DIAGNOSIS 87 



was in any way pathogenic. The first case tended towards con- 

 stipation, which had to be relieved by repeated doses of salts. The 

 second case was also treated in this way while in hospital. 



Description of the Living Flagellate. The living flagellate 

 (Plate IV, figs. 1 to 6)* is a small active oval organism which dances 

 about amongst the faecal matter by means of its two flagella of 

 different strength and action. The long, thin, anterior flagellum 

 lashes about continuously and propels the flagellate through the 

 liquid, while the stouter and shorter flagellum which projects from 

 the cytostome may work either regularly, but at a different rate 

 from the anterior one, or irregularly with periods of rest alternating 

 with periods of activity. This independent action of the stout 

 cytostome flagellum, especially when its action is intermittent, 

 gives a peculiar jerky movement to the anterior end of the flagellate 

 as it swims forward under the regular action of the long anterior 

 flagellum. In cover-glass preparations the flagellate has a peculiar 

 habit of applying itself to the surface of the cover-glass or slide to 

 which it adheres. In this position the action of the two flagella 

 can be easily studied, and it is in this side view attitude that the 

 flagellate reminds one so forcibly of the body outline of a bird. 



In shape the flagellate is ovoid with the anterior end rounded 

 and the posterior end pointed. There is a cytostome at the side 

 of the anterior end, while the tapering part of the posterior end 

 tends to be on the side of the body opposite to that on which the 

 cytostome opens. This arrangement makes the flagellate bilaterally 

 symmetrical. From the anterior end, but slightly nearer the 

 cytostome side of the body, there takes origin a thin flagellum 

 which equals the body in length. A second stouter and shorter 

 flagellum arises from the inner part of -the anterior wall of the 

 cytostome. It passes slightly backwards and outwards through the 

 mouth of the cytostome, from which it projects for a considerable 

 distance. The separate action of the two flagella has been 

 explained above. The cytoplasm of the flagellate body is very pale, 

 much paler and less refractile than that of small forms of tetramitus 

 or trichomonas. It is frequently much vacuolated and the vacuoles 

 contain bacilli or cocci which have been ingested. One can often 

 see quite large bacilli entering the cytostome. The nucleus occupies 

 the anterior end of the body and in the living flagellate can hardly 

 be detected except as a clear, more homogeneous area which is 

 devoid of the granulations or vacuoles of the rest of the body. 

 The length of the body varies from 4 to 9 microns, the majority 



* See inset between pages 148 and 149. 



