ANIMAL PARASITES 113 



saves the expensive use of absolute alcohol. It consists of 

 carbolic acid (melted crystals), 1 part; xylol, 3 parts. 



Schaudinn's Fluid. — This invaluable fixing fluid for Protozoa 

 consists of: saturated aqueous solution of corrosive sublimate, 

 65 parts; 95 per cent alcohol, 33 parts; glacial acetic acid, 2 

 parts. The corrosive sublimate solution is kept in stock and 

 the mixture is made immediately before use. It may be used 

 cold but better results are obtained by heating until steam begins 

 to rise before putting the films into it. As with other corrosive 

 sublimate mixtures, iodised alcohol should be used for washing. 



Bouin's Picro-formol. — Saturated aqueous solution of picric 

 acid, 30 parts; formalin, 10 parts; glacial acetic acid, 2 parts. 

 Langeron, who regards this as a universal fixer, keeps a stock 

 solution of 1 part of formalin and 3 of water saturated with 

 picric-acid crystals. To this he adds 5 per cent of glacial acetic 

 acid just before use. Tissues may be fixed for from 2 to 3 days 

 to a week and are then placed in 80 per cent which is changed 

 several times. 



Brasil's Picro-formol is an alcoholic modification of Bouin's 

 fluid which possesses great penetrating powers. Used warm, 

 it is especially good for cysts. Eighty per cent alcohol, 150 cc. ; 

 formalin, 60 cc; glacial acetic acid, 15 cc; picric acid, 1 gram. 



Zenker's Fluid. — Potassium dichromate, 2.5 grams; corrosive 

 sublimate, 5 grams; water, 100 cc; and add before using glacial 

 acetic acid, 5 cc. Fix for 12 to 48 hours and wash in running 

 water for an equal period, transfer to 70 per cent alcohol for 1 

 day, then to 80 per cent iodised alcohol to remove the corrosive 

 sublimate. It is advisable to keep the tissues in the dark while 

 in the alcohol. 



Delafield's Haematoxylin. — Saturated aqueous solution of 

 ammonia alum, 100 cc; stock solution of hematoxylin (10 per 

 cent in 95 per cent alcohol), 20 cc. Leave it exposed to the 

 light and air in an unstoppered bottle for 3 or 4 days, filter, and 

 add glycerine, 50 cc, and methyl alcohol, 50 cc Let stand 

 uncorked for a week or more, until the color is sufficiently dark ; 

 then filter. Solutions which have ripened for several months 

 are best. For ordinary staining the solution should be diluted 

 with 3 to 4 volumes of distilled water, but for staining tapeworms 

 and flukes it may be so dilute as to have only a faint purple 

 color and be allowed to act for 24 hours or more. If necessary 

 to destain by the use of acid alcohol, follow this by alcohol made 



