1917] Boeck: Protozoan Cysts in Mammalian Faeces 147 



ill the application of this stain. In the first, one gram of faecal 

 material in thirty cubic centimeters of normal saline solution is 

 emulsified by means of the electric mixer for about eight minutes. 

 About five cubic centimeters of neutral red solution N/10,000 are then 

 put into the emulsion, which is stirred until it is of a uniform reddish 

 color. Five centimeters of ether are then stirred into the emulsion. 

 The remaining steps of the process of concentration follow at once. 



In the second method of application of this stain, a drop of the 

 neutral red solution may be applied to a very small amount of residue 

 containing the cysts and placed on a slide, preparatory to microscopic 

 examination. The residue is obtained by centrifuging the saline solu- 

 tion which had been drawn off at the bottom of the separatory funnel. 

 In the latter method of application of the solution of neutral red 

 there results a greater intensification of the stain in the debris, afford- 

 ing a sharper contrast between debris, yeasts, and the cysts. The 

 cysts may take at the most only a light pink stain, due to their wall, 

 which prevents penetration of the reagent. In many cases the cysts 

 are not colored at all, even by this intensive method of treatment. 



The use of this stain, however, helps to cut short the time necessary 

 for making the examination, since one is able to detect the cysts with 

 great celerity and accuracy because of the sharp contrast that is 

 presented between the cysts, the yeasts, and the debris. The yeasts, 

 on the other hand, are usually entirely stained, but if not, the stain 

 can be seen in the central vacuole, which at once differentiates the 

 yeasts from protozoan cysts of the same size in which the structure 

 of the contained organism may be indistinct. Since, however, only 

 a slight amount of stain is wont to differentiate the internal structures 

 of protozoan cysts, one is able by the use of the neutral red to dis- 

 tinguish the nuclei, axostyle, and the remains of the intracytoplasmic 

 flagella in the cysts of (riarcUa more quickly than without the use of 

 the stain. It is this feature which adds to accuracy in the detection 

 of these cysts. 



The method in full as I have been using it is as follows : Take 

 at least one gram of the stool to be examined, place it with thirty 

 cubic centimeters of normal saline solution in the mixing glass and 

 stir for at least ten minutes, pouring in five cubic centimeters of 

 neutral red solution N/10,000 at the end of eight minutes, if one 

 desires to use the stain at this time in the method. At the end of ten 

 minutes, while still stirring, add five cubic centimeters of ether and 

 stir two or three minutes longer. 



