TRICHOMONAD FLAGELLATES. 291 



been found to be of little \-alue for accurate morphological or cyto- 

 logical study. 



The region of greatest infection is the junction of the large and 

 small intestine and the upper part of the rectum. Other organs of 

 the body have been examined including the lungs, spleen, liver, 

 genitalia, etc., but in no instance have flagellates been found outside 

 the digestive tract. Occasionally a few have been found in the 

 stomach and more often in the small intestine, but their normal 

 presence here has been uncertain in any case because of possible 

 contamination through dissection, and scanty in every case. In 

 the lower part of the rectum the parasites were usually not abundant. 



The division cycle in these flagellates occurs at infrequent intervals 

 and is often not observed until the stained preparations are examined, 

 or at least until it is too late to make more smears from the same 

 material. It is therefore important when investigating the life 

 histories of these flagellates, to make as many preparations as the 

 material will allow, or as can be conveniently handled, even though 

 many of them are afterwards discarded. 



Various fixing agents have been tried, Flemming's fluid and picro- 

 mercuric being excellent, but hot Schaudinn's fluid, with a few drops 

 of acetic acid added, has given the best results. The material to be 

 examined was smeared over the cover glass and this was placed, film 

 downward, on the surface of the fixing fluid, and left in that position 

 for about five minutes when it was inverted and placed in 50% alcohol 

 with successive changes to 100% alcohol. If the intestinal wall was 

 not covered with sufficient fluid it was moistened slightly with normal 

 salt solution before smearing it on the cover glass, and if the amount 

 of liquid on the cover glass was too great it was allowed to evaporate 

 till nearly but not quite dry before placing the smear in the fixing 

 fluid. The material was found to adhere to the cover glass more 

 firmly when it was not plunged beneath the surface of the fixing fluid 

 for the first few minutes at least, but remained floating on the surface. 



By far the best results in staining were obtained with iron haema- 

 toxylin. Heidenhain's method was used at first but later alcoholic 

 solutions were substituted for the aqueous solutions, and these gave 

 very satisfactory results and saved time. The stock solution of ^% 

 iron haematoxylin was diluted with ten parts of 70% alcohol. For the 

 mordant the stock solution of 4% iron alum was diluted with ten 

 parts of 50% alcohol. The iron alum will not remain long in solution 

 in alcohol so the solution must be renewed frequently. The prepara- 

 tions were left in this for 10 minutes, rinsed in 50% alcohol and placed 



