APPENDIX. 359 



to twist and bend from side to side with great activity. 

 The organism can turn completely round with lightning 

 rapidity, so that the flagellum, at one moment lashing 

 in one direction, is suddenly observed working in the 

 opposite direction. Then suddenly the organism makes 

 progression, and it can be distinctly seen to move in the 

 direction of tJte flagellum, thj flagellum threading its way 

 between the corpuscles and drawing the rest of the organism 

 after it. By treating cover-glass preparations with osmic 

 acid, the appearances corresponded exactly with photo- 

 graphs of the organisms observed by Lewis in India, so 

 that the author has no doubt of their identity, in spite of 

 the descriptions not completely according. A great like- 

 ness to the organisms described by Mitrophanow, and to 

 the Surra parasite, as just described, was obvious ; and 

 after staining the rat parasites the closest examination 

 confirmed the belief that they were morphologically 

 identical with the stained parasites of Surra. 



The cover-glasses with a thin layer of blood should be 

 passed through the flame of a Bunsen burner in the way 

 commonly employed for examining micro-organisms, and 

 stained with an aqueous solution of fuchsine, methyl-violet, 

 or Bismarck brown. The following method will, how- 

 ever, be found most instructive. Use freshly-prepared 

 saturated solution of fuchsine or methyl-violet in absolute 

 alcohol, and put a drop with a pipette on the centre of the 

 preparation ; do not disturb the drop-form for a few 

 moments ; then, before the alcohol has evaporated, wash 

 off the excess of stain. It will be found that where the 

 drop rested the organisms will be very deeply stained, 

 while in the surrounding area the colour will vary in 

 intensity. 



By the effect of the different degrees of staining much 

 may be learnt (Fig. 135). In one organism the body and 

 entire membrane will be equally stained ; in another the 

 margin of the membrane only. In some the posterior 

 stiff filament is stained, and at its base a darkly-stained 



