650 AMOEBIC DYSENTERY 



examination of the fasces after being passed is not essential, as 

 the cysts persist unchanged for several days. 



For permanent preparations dried films are not suitable, as in 

 the preparation of these the entamoebas become distorted. Wet 

 films should be used, and a very suitable fixing agent is composed 

 of 2 parts of a saturated solution of corrosive sublimate in normal 

 salt solution and 1 part of absolute alcohol ; they are then 

 treated as already described (p. 93). For such films Heiden- 

 hain's iron hsematoxylin has been found to be one of the best 

 stains, but ordinary hsemalum gives quite good results. 



In sections of tissue the entamoebas may be stained by methy- 

 lene-blue, by safranin, by haematoxylin and eosin, iron haama- 

 toxylin, etc. Benda's method of staining with safranin and 

 light-green is also a very suitable one. Sections are stained for 

 several hours in a saturated solution of safranin in aniline oil 

 water (p. 103), they are then washed in water and decolorised 

 in a \ per cent, solution of light-green in alcohol till most of the 

 safranin is discharged, the nuclei, however, remaining deeply 

 stained. In this* method the nuclei of the entamoebas are 

 coloured , red (like those of the tissue cells), the protoplasm 

 being of a purplish tint. 



