METHODS OF EXAMINATION 649 



Methods of Examination. The faeces in a case of suspected 

 dysentery ought to be examined microscopically as soon as 

 possible after being passed, as the amoebae disappear rapidly, 

 especially when the reaction becomes acid. A drop is placed 

 on a slide without the addition of any reagent, a cover-glass is 

 placed over it but not pressed down, and the preparation is 

 examined in the ordinary way or on a hot stage, preferably by 

 the latter method, as the movements of the amoebae become 

 more active, and it is difficult to recognise them when they are 

 at rest. Hanging-drop preparations may also be made by the 

 methods described. Dried films are not suitable, as in the 

 preparation of these the amcebae 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. 96). For such films Heiden- 

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

 stains. In sections of tissue the amoebae may be stained by 

 methylene-blue, by safranin, by haematoxylin and eosin, and 

 iron haematoxylin, 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. 106), they are then washed in water and decolorised 

 in a J 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 amcebae are coloured 

 red (like those of the tissue cells), the protoplasm being of a 

 purplish tint. 



