OF THE ALIMENTARY TRACT 135 



and tapering posterior extremities. A lateral view 

 shows the broad concave indentation anteriorly and 

 ventrally. It swims with a peculiar vibratory mo- 

 tion of the body and frequently flexes the tail to the 

 anterior end. Chilomastix has a stiff inflexible body 

 of the shape of a carrot. It swims in a character- 

 istic ^'corkscrew" forward. Trichomonas has a typi- 

 cal darting motion, moving very rapidly when most 

 active, frequently stopping and anchoring by its pos- 

 terior end to a clump of debris, while it whips the 

 solid particles about with its flagella in violent man- 

 ner. It has a very flexible plastic body, twisting 

 and turning, crawling among masses of solid parti- 

 cles. The undulation of its surface '^ruffle" is most 

 characteristic. When specimens have been exposed 

 for a time and become sluggish. Trichomonas de- 

 velops an undulating movement of the surface of the 

 body, probably a slow movement of a relaxed un- 

 dulating membrane, and the flagella may move so 

 slowly that they can be readily seen or even counted. 

 In such a state Giardia and Chilomastix remain rigid, 

 their form and shape does not change, their flagella 

 gradually cease motion, hanging as idle threads, while 

 the undulating flagellum within the ventral groove 

 may continue a sinuous motion. 



Most painstaking study and carefully stained 

 specimens are necessary for identification of the un- 

 common more minute species, Einbadomoiias intes- 

 tinalis, Tricercomonas intestinalis and Enter omonas 

 hominis. 



