FORMALIN-ALCOHOL 



131 



FROZEN SECTIONS 



In combination with other reagents 

 formalin is also a good fixative cf. For- 

 malin-Zenker in which formalin is sub- 

 stituted for acetic acid, Bouin, Regaud's 

 Fluid and many others. Since, how- 

 ever, formalin is a strong reducing agent 

 mixtures of which it is a part are un- 

 stable so that it must be added immedi- 

 ately before use. As Mallory (p. 40) 

 points out, formalin also has certain 

 disadvantages. It is inferior to alcohol 

 as a preservative for iron and other 

 pigments. It often changes the color of 

 bile concretions from yellow to green and 

 it may produce in the tissues a trouble- 

 some brown-black finely divided crystal- 

 line precipitate from laked hemoglobin. 

 He advises removal of this precipitate 

 by treating sections for 30 min. in 75% 

 alcohol, 200 cc; plus 25-28% ammonia 

 water, 1 cc. (Schridde's method), or for 

 10 min. in 80% alcohol, 100 cc. plus 1% 

 aq. potassium hydroxide, 1 cc. (Vero- 

 cay's method) after either of which they 

 are washed thoroughly in water before 

 placing in 80% alcohol and staining. 

 When employed as a preservative con- 

 centration of formalin should be 4%. 



Formalin-Alcohol, see Alcohol-Formalin. 



Formalin-Zenker. Zenker's fluid modified 

 by substituting 5% formalin in place of 

 the 5% acetic acid. It is also known 

 as Helly's fluid and Zenker-formol. 

 This is one of the three major routine 

 fixatives the others being Zenker and 

 Bouin. See Acid Fast Bacilli, Alveolar 

 Pores, Arteries, Basal Bodies, Brazilin- 

 Wasserblau, Mucus, Goodpasture's 

 Method, Methyl-Green Pyronin. In 

 some cases 10% formalin is inserted 

 instead of 5%. 



Formalose see Formalin. 



Formamide of Eastman Kodak Co. is a sub- 

 stance, called a "modifier", which when 

 added in 10% to 50% alcohol improves 

 fixation and staining of peripheral nerve 

 (Bank, E. W. and Davenport, H. A., 

 StainTech.,1940, 15, 9-14). 



Formazan, see Triphenyltetrazolium Chlo- 

 ride. 



Formic Acid, see Decalcification. 



Formol is a synonym for formalin. 



Formol-Miiller, This is 1 part of formol to 

 10 parts MuUer's fluid. 



Formol-Nitric fixative. 3 parts 10% for- 

 malin and 1 part 10% nitric acid. This 

 has, according to McClung, proved very 

 valuable for chick embryos. 



Formol-saline is the fluid resulting when 

 formalin is diluted with isotonic salt 

 solution (presumably 0.85% aq. sodium 

 chloride) instead of with aq. dest. It is 

 not advised as a fixative. 



Formvar, a plastic occasionally employed 

 to make supporting films in electron 



microscopy. It is made by Shawinigan 

 Products Corporation, New York, N. Y. 



Fowl Pox, see Borrel Bodies. 



Fractionation, see collection of cell com- 

 ponents under Centrifugation. 



Fractures. Vital staining with Alizarin 

 Red S (Schour, et al., J. Dent. Res., 

 1941,20,411-418). 



Fragility Tests. Micro for erythrocytes 

 (Kato, K., J. Lab. & Clin. Med. ,1940, 

 26, 703-713. See Capillary Fragility Tests. 



Freezing. Details on the formation of 

 ice within cells are given by Chambers, 

 R. and Hale, H. P., Proc. Roy. Soc, 

 B, 1932, 110, 336. See Revival after. 



Freezing and Drying, see Altmann-Gersh. 



Freifeld's Blood Stain. To 20 cc. tap water 

 add 7 drops Ziehl's Carbol Fuchsin 

 and 5 drops 1% aq. methylene blue. 

 Stain methyl alcohol fixed blood smears 

 1 hr. Shows clearly basophilic granules 

 of toxic neutrophiles (Naegeli, O., 

 Zlutkrankheiten und Blutdiagnostik, 

 Berlin, 1931, p. 19, quoted from Mc- 

 Clung, 1950, p. 225). 



Frozen Sections. These are of great value 

 when preparations must quickly be 

 made and when methods of alcoholic 

 dehydration before sectioning are contra- 

 indicated. They are specified elsewhere 

 in this book under several headings 

 including : 



Amyloid Lipase 



Cholesterol Lipids 



Digitonine reaction Microglia 



Dopa oxidase Millon's reaction 



Gold Oxidase 



Indigo-carmine Pepsin 



Krajian'a Congo stain Spirocheta pallida 



Liebermann-Burchardt Urease 



To make the sections take recently 

 excised still living tissue, or better fresh 

 tissue fixed for about 30 min. in 10% 

 formalin. First freeze a little water on 

 the block of a freezing microtome. 

 Then add the tissue and freeze it too 

 plus a drop more of water. Allow block 

 to thaw to optimum consistency, cut 

 sections 15-50m thick as desired, and 

 remove them with a camel's hair brush 

 from the microtome knife to formalin, 

 water or physiological saline. When 

 many are required, it may be necessary 

 to freeze several times as the tissue be- 

 comes too soft. If thinner sections are 

 wanted resort to Gelatin Imbedding 

 before sectioning. 



For quick staining Thibaudeau, A. A., 

 J. Lab. & Clin. Med., 1933, 19, 204-209 

 advises that sections of formalin fixed 

 tissue be stained in Harris' hematoxylin 

 5-15 sec, rinsed in aq. dest., blued in 

 aq. dest. -f few drops NH4OH, passed 

 up through 70, 85 and 95% alcohol 

 counterstained in absolute alcohol and 



