STRUCTURE AND DIVISION OF TRICHOMONAS 131 



illustrates this point. In this case the entire set of instruments, 

 reagents, glassware, microscope, etc., were placed in a warm 

 room at 37°C. a number of hours before the mouse was killed. 

 The mouse was taken into the same warm room, killed, opened, 

 and the coecal contents examined. The coecum was found to 

 be swarming with Trichomonas, so fixations were made with 

 Allen's, Bouin's, Carnoy's, Schaudinn's, sublimate-acetic and 

 weak Flemming's fluids. After fixing for half an hour at 37°C., 

 the subsequent washing and further treatment were carried out 

 at room temperature, and all the slides were stained at the same 

 time and in the same way with the same stock solutions of iron 

 alum and haematoxylin. The chemical differences in the differ- 

 ent fixatives would therefore appear to be the variable factors 

 in this experiment, so that differences in appearance can, I think, 

 be attributed to different effects of the fixatives on the organisms. 

 In any smear of this kind, of course, there are always thicker 

 and thinner areas, and the intensity of the stain varies with the 

 thickness of the film on the cover-glass. It is therefore possible 

 to compare for a wide range of intensities of the stain. 



The general cytoplasm may first be considered. Figure 1 

 indicates the results from fixation with Carnoy's fluid. Little 

 vacuohzation is indicated, and such vacuoles as there are do not 

 show any stainable contents. Figure 2 is from a smear fixed 

 in sublimate-acetic, and here not only are the vacuoles well 

 defined, but the contents have taken the stain. Some few 

 individuals on this smear did not show the vacuole contents 

 stained, but the great majority did. The smears of this series 

 fixed in Schaudinn's fluid showed an occasional individual with 

 vacuole contents stained. In the other series which were fixed 

 with Schaudinn's fluid vacuole contents did not usually take the 

 stain. Figure 3 is from a smear fixed in weak Flemming's fluid, 

 and the structure of the protoplasm is much like that in figure 1. 



The various organelles may next be considered. Schaudinn's 

 fluid and sublimate-acetic gave somewhat similar results except 

 for the protoplasmic vacuoles already mentioned. The nucleus, 

 blepharoplast, posterior flagellum, chromatic basal rod, and 

 specific granules are all sharply differentiated, although in the 



