AMCEBIC DYSENTERY 587 



measurements may be made, is a useful adjunct. Dark ground 

 illumination is of considerable assistance in the diagnosis of 

 flagellates. 



2. Donaldson l recommends the following method for examina- 

 tion of faeces for entamceba cysts. The following solutions are 

 used : 



A. Five per cent, aqueous solution of potassium iodide 

 saturated with iodine. At time of using mix with an equal 

 volume of either of the following solutions, B : 



B. (1) A saturated aqueous solution of rubin s. ; or 



(2) A saturated aqueous solution of eosin ; or 



(3) Stephens's scarlet writing fluid. 



A few loopfuls of one of the above stain mixtures are placed on 

 a clean slide, a loopful of faeces is taken and is rubbed up with the 

 stain to form a uniform suspension, and a clean cover-glass is 

 gently lowered over the drop. No gross particles must be left 

 in the emulsion. Amoebic cysts (both varieties) stand out as 

 brilliant yellow or greenish-yellow spheres in a more or less 

 uniform red background. The nuclear structures in the cyst 

 stand out prominently. Other protozoal cysts, plant hairs and 

 mould spores also stain yellow, Blastocystis stains reddish. 



3. Cropper and Kow 2 describe a method for concentrating 

 Entamceba cysts. One gramme of faeces is shaken in a mechani- 

 cal shaker with 30 c.c. of saline in a bottle of 120-150 c.c. capacity 

 for at least half an hour until thoroughly disintegrated. The 

 suspension is then poured into a separating funnel, and shaken up 

 by hand for half a minute with 10 to 20 per cent, of its volume 

 of methylated ether, after which the mixture is allowed to stand 

 for a minute or two in the funnel until the two liquids have 

 separated. The faecal debris float in the upper ethereal layer, 

 the cysts remain in the lower saline layer. The latter is then 

 drawn off from the funnel and is centrifuged at low speed for 

 two or three minutes ; experience will give the precise time and 

 speed. The cysts are now concentrated in the deposit, and a 

 concentration of fifteen times may thus be obtained. 



4. Probably Heidenhain's iron-haematoxylin method is the best 

 for staining this and other protozoa : 



(a) Make smears of the material and drop while wet into the 



1 Lancet, 1917, vol. i, p. 571. 

 2 Lancet, 1917, vol. i, p. 179. 



