272 THE PROTOZOA 



% inch from the vaselined line and a suitable portion of the faeces to be examii 

 is emulsified in it. The edge of a square cover-glass is then applied to the vaselined 

 line and allowed to drop on the preparation. By pressure suitable thicknesses of 

 fluid can be examined. There is an absence of current motion. Better, when access- 

 ible, is it to use the dark field illuminator as in this way the flagella are distinctly 

 brought out. The india ink method is also applicable. Staining of smears by 

 Giemsa's method, following fixation in methyl alcohol or 5% formalin solution is 

 more satisfactory for flagellates than for amoebae, which, as before stated, should 

 be fixed in moist smears and stained by haematoxylin. This method of mounting 

 in iodine solution, however, is the one I always use for encysted amoebae. 



The intestinal flagellates are classified according to number of 

 flagella, absence or presence of an undulating membrane and of a 

 blepharoplast. Three of these flagellates are but rarely found in the 

 stools and seem to be of little importance. They are (i) Cercomonas, 

 which has a single nucleus with one free flagellum and a second one 

 which turns backward to be attached to the body and then projects 

 posteriorly as a second free flagellum, (2) Bodo, which has a single nuc- 

 leus, but two anteriorly projecting flagella and (3) Prowazekia which 

 has, besides the nucleus, a blepharoplast from which arise two flagella. 

 These flagellates can be cultivated on media used for the cultural 

 amoebae and it is thought by some that they at times show amoebae- 

 like stages. 



There is an organism, supposed to belong to the moulds, which may be mistaken 

 for an encysted flagellate. It is called Blastocystis hominis and has a large central 

 vacuole with a refractile narrow rim which contains one or more nuclei. When 

 stained by Giemsa's stain the central part is very faintly stained while the rim is 

 deep blue. 



Trichomonas intestinalis. This is a very common parasite in diarrhceal stools 

 but as to its pathogenicity there is much doubt. It is pear-shaped and about 9 by 

 14 microns. There are three flagella projecting anteriorly with a fourth one bordering 

 an undulating membrane and projecting posteriorly. It has a cytostome near the 

 nucleus. There is also a T. vaginalis which is found in vaginal secretion of acid 

 reaction, disappearing when the reaction becomes alkaline as at the time of 

 menstruation. It is somewhat larger than the intestinal form and is not infre- 

 quently found in urine. 



Tetramitus mesnili. This flagellate differs from the preceding one in not having 

 an undulating membrane or fourth flagellum. The three anteriorly projecting 

 flagella are long and slender. There is a very prominent long slit-like cytostome 

 within which is a flagellum. The nonflagellate end is very much attenuated. 



This parasite has been reported not infrequently as a cause of diarrhceal condi- 

 tions since its first reporting by Wenyon in 1910. 



All the above-mentioned flagellates are found in the large intestines especially in 

 the region of the caecum. 



