182 PROTOZOAN PARASITISM 



is the cyst which must be depended upon for appear- 

 ance. 



In case of their presence, duodenal or trans-duo- 

 denal biliary drainage usually shows the trophozoites, 

 not the cysts, in the duodenal content removed. The 

 parasite became very prominent in the course of 

 the recent commonly practiced trans-duodenal bili- 

 ary drainage. The writer has seen it frequently in 

 such material. Hollander (1923) found it in nine 

 of one hundred and seventy such examinations. This 

 is, however, not necessary as a measure for this pur- 

 pose only. 



The trophozoite has a form so characteristic that 

 it should take only a picture of it to lead to identifi- 

 cation on first observation. If a pear were split in 

 halves longitudinally and inverted and the anterior 

 half of the split surface scooped out to a shallow con- 

 cavity, one would have the form of an inert organism. 

 Assume that body as flexible and attach at the proper 

 places four pairs of long flagella, which in movement 

 cause the organism to vibrate rapidly as it swims and 

 flexes its body, and one has the form and action of the 

 organism. 



The size of the active form is about 10 to 20 microns 

 long by about half that width. Seen anteropos- 

 teriorly it is pearshaped. In lateral view the dor- 

 sal surface is convex forward and concave behind, the 

 outline being a shallow S, while the ventral side shows 

 the forward depression of the oral sucker, and a grad- 

 ual tapering from its border to the tail, this in the 



