580 PROTOZOA 



is more penetrating, and therefore better for fixing arthropods 

 containing parasites ; also cysts, etc., especially when used warm. 



Grasse {Arch. Zool. Exper., Ixv, 1926, p. 349) recommended 

 McClung's modification of Bouin's mixture for flagellates (§ 115). 



For other protozoa urea is said to have little or no value, 



1140. Hollande's Cupro-picro-formol-acetic Mixture is also said 

 to be good for flagellates, and to be more penetrating than ordinary 

 BouiN {Arch. d\4nat. micr., xviii, 1921, p. 96) : 



Picric acid ..... 4 grm. 



Neutral copper acetate . . . 2-5 ,, 



Formol , . . . . .10 c.c. 



Glacial acetic acid . . . . 1-5 ,, 



Distilled water ..... 100 ,, 



1141. Carnoy's Mixture (§ 90). Fix films ten to fifteen minutes, 

 blocks of tissue a quarter to one hour, and wash out in 90 per cent, 

 alcohol. 



This mixture, one of the most penetrating fixatives known, 

 is excellent for showing up the chromosomes of even large protozoa 

 mounted whole, since it dissolves many cytoplasmic inclusions 

 without destroying chromatin. It is a good fixative for glycogen, 

 which is precipitated and can then be well shown up with Best's 

 stain, § 670. 



1142. Flemming's Fluid (§ 44). Fix thin films for about ten 

 minutes. Penetration is very poor ; therefore pieces of tissue 

 must be small — fix one to twenty-four hoiu's and wash in running 

 water for about half as long before dehydrating. 



MiNCHiN {Quart. Journ. Micr. Sci., Ix, 1914, p. 506) found this 

 the best fixative for stomachs of fleas full of rat blood and trypano- 

 somes ; the histology of the wall was extremely good and the 

 blood not shrunk away from it, and both free and intracellular 

 trypanosomes well preserved. 



1143. Flemming without Acetic. For various modifications of 

 Flemming for fixing the cytoplasm and its inclusions without 

 destroying mitochondria, etc., see § 693. For other similar 

 fixatives, see under Cytology, § 679. 



1144. Osmic Vapour. An excellent fixative, to which films on 

 coverslips may be exposed. It is used chiefly by protozoologists 

 for smears of minute flagellates and other parasites, especially 

 in blood. 



MiNCHiN used the following method for smears (ibid., liii, 

 1914, p. 755) :— 



In a suitable glass slide tube place some pieces of glass rod, 

 on which the slide can rest when the tube is tightly closed with 

 a stopper. Into the bottom of the tube put 20 drops of 4 per 

 cent, osmic acid solution with 1 drop of glacial acetic acid. This 

 tube, if kept in the dark and tightly closed, can be used repeatedly. 



To fix the smear, place the slide in the tube and close for ten 



