PROTOZOA 570 



1135. Sublimate-picric mixture recommended by Yocum {Calif. 

 Publ. ZooL, xviii, 1918, p. 342) :— 



Mercuric chloride .... 2 grm. 



Picric acid . . . . . 1 ,, 



95 per cent, alcohol . . . .110 c.c. 



Ether 20 „ 



Acetic acid (glacial) . . . . 20 ,, 



Formol (40 per cent. HCHO) . . 50 „ 



Such a mixture of oxidising and reducing agents would not be 

 likely to keep. Presumably the formol is only added just before 

 use. 



Taylor uses this fixative hot for Eiiplotes (ibid., xix, 1920, 

 p. 417), and then stains with Mallory's triple stain haematoxylin or 

 for demonstrating the fibrillar apparatus. Hammond {Quart. 

 Journ. Micr. Sci., Ixxix, 1937, in press) also uses it for this purpose, 

 but prefers simpler sublimate mixtures before silver impregnation 

 methods for showing up silver line systems in ciliates. 



1136. Sublimate-bichromate. Zenker's mixture (§ 78) is said 

 by DoBELL and O'Connor {Intestinal Protozoa of Alan, 1921, 

 p. 138) to give excellent results with intestinal protozoa, free or^ 

 in tissues, but often fails to penetrate cysts properly. 



If a piece of tissue is large enough to require several hours' 

 fixation, it will have to be washed for several hours in gently 

 running water to remove excess of bichromate before removing 

 the excess sublimate in the usual way. 



1137. Bichromate-acetic. Tellyesniczky's formula (§ 57) is 

 used by Dehorne {Arch. Zool. Exper., Ix, 1920, p. 47) to fix 

 Paramoecium and Colpidium. 



1138. Picro-formol-acetic or Bouin's Fluid, § 115. 



Fix films ten to forty minutes ; tissues for not more than 

 twenty-four hours. Wash out with 70 per cent, alcohol. 



A very good fixative for protozoa and tissues, but it sometimes 

 fails to penetrate cysts and spores. 



DoBELL suggested substituting a saturated solution of picric acid in 

 90 per cent, alcohol for the aqueous solution in Bouin's formula, and 

 adding 1 to 2 drops of chloroform just before use to facilitate penetra- 

 tion of chitin. Hoare (Parasit., xv, 1923, p. 374) found this modifica- 

 tion of the fixative excellent for sheep keds containing trypanosomes. 

 He kept the insects in the fixative for twenty-four hours (one hour 

 warmed on the incubator, twenty -three at room temperature). He 

 then placed them in 90 per cent, alcohol for seven days (changing the 

 alcohol from time to time). 



1139. Duboscq-Brasil modification, or alcoholic Bouin : 

 Alcohol (80 per cent.) . . . .150 c.c. 



Formol . . . . . . 60 ,, 



Glacial acetic acid . . . . 15 ,, 



Picric acid ..... 1 grm. 



19—2 



