CHAPTER XXX VI. 539 



to form a fairly smooth emulsion, and a clean coverslip gently 

 lowered on to the drop. In order to get the best possible definition, 

 it cannot be emphasised too strongly that the film so made should 

 be spread out under the cover-glass by capillarity so as to form the 

 thinnest layer possible, preferably a layer which is no thicker than 

 the diameter of an Entamoeba coli cyst. 



The exact amount of stain to be used will soon be learned after one 

 or two attempts, and depends upon the size of the loop employed and 

 the size of the coverslip. It is a matter of considerable importance 

 the way in which the film is made, especially where Rubin S., or, to a 

 less extent, eosin has been used in the staining combination, for if the 

 layer of fluid between the slide and coverslip be too thick the super- 

 fluous film of fluid overlying the cysts tends to render the latter less 

 bright. In the case of cysts of the size and shape of Entamoeba coli 

 or histolytica, this makes little difference, but if one is hunting specially 

 for the Lamblia, or, still more, Tetramitus mesnili, the colour contrast 

 is not so marked, owing to the smaller size of the cysts and the conse 

 quent thicker red layer of fluid overlying them. Where the worker has not 

 acquired sufficient dexterity in making such a film, the difficulty may 

 be got over by using Rubin S. or eosin of only half saturation in the 

 stain combination, or by employing the scarlet writing fluid mentioned. 

 In this way the effect of the super -imposed deeper red is to some extent 

 obviated. In a wet preparation stained by this method there is a more 

 or less homogeneous red background, from which the cysts stand out 

 as brilliant yellow or greenish- yellow spheres which even the tyro cannot 

 miss seeing. 



1017. Method for the Tsetse Flies (M. ROBERTSON, Trans. Eoy. Soc., 

 Series B, vol. 203, p. 161 ). The newly hatched flies are starved for twenty- 

 four to thirty-six hours and are then fed on the infecting monkey once, 

 or in some cases twice. The infecting feed is the first blood ingested 

 by the flies. After the infecting feed the cage is starved for one or two 

 days and thereafter fed on clean monkey's blood every second or third 

 day. Daily feeding is not essential to the welfare of glossina, and does 

 not appear to occur in nature. Dissections are made in a drop of physio- 

 logical salt solution. The trypanosomes are studied both in the live 

 state and in fixed and stained preparations. Preserved material is 

 fixed while wet by dropping the coverslip film side downwards into 

 Schaudinn's solution ; the preparations are subsequently stained by 

 Heidenhain's iron hsematoxylin. 



1018. Immobilisation. See the narcotisation methods 20 to 25. 

 According to SCHURMAYER (Jen. Zeit., xxiv, 1890, p. 402), nitrate 



of strychnin, of 0-01 per cent, or less, gives good results with some 

 forms, amongst which are Stentor and Carchesium. Antipyrin 

 (0 -1 per cent.), or cocaine of -01 per cent., seems only to have given 

 good results as regards the extension of the stalk in stalked forms. 

 EISMOND (Zool. Anz., xiii, 1890, p. 723) slows the movements of 



