FERRIC CHLORIDE — FUCHSIN 30I 



Ferric Chloride. — An aqueous solution is used as a test for 

 tannin. When sections containing tannin are placed in this 

 solution on the slide, a color is produced which may vary from 

 dark' blue to green. 



Ferricyanide of Potassium. — Used in demonstrating the 

 structure of pyrenoids. Algae containing pyrenoids are placed 

 in a mixture of equal parts of a lo per cent, solution of ferri- 

 cyanide of potassium and a 55 per cent, solution of acetic acid, 

 and then treated as described under Dahlia. 



Fixatives and Fixation. — See page 258. 



Fischer's Method of Demonstrating Cilia. — The following 

 method is highly recommended for demonstrating cilia of cer- 

 tain bacteria: An exceedingly small amount of the culture con- 

 taining the bacteria is spread out as thinly as possible on the cover- 

 glass. After the film has dried on the coverglass' the latter is 

 passed through the flame of an alcohol lamp or Bunsen burner 

 (care being taken to avoid a too excessive heat), and then a few 

 drops of a mordant are put on the film on the coverglass. The 

 mordant is prepared by dissolving 2 gm. of tannin in 20 c.c. of 

 water. The coverglass is then passed back and forth over a 

 small flame until vapor arises from the mordant. The mordant 

 is now washed off by means «f water from a wash-bottle, and 

 then one edge of the coverglass is held in contact with a piece of 

 filter paper to draw away the surplus watei:. Next, a concen- 

 trated aqueous solution of fuchsin is spread over the film on the 

 coverglass, and the coverglass is held over a flame until the fuch- 

 sin solution begins to boil; the coverglass is then washed off, and 

 is allowed to dry. At any time thereafter the coverglass, with 

 the film side down, may be cemented to the slide with balsam.. 

 In successful preparations made by this method cilia, when pres- 

 ent, will stand out quite sharply. 



Fuchsin. — Dissolve i gm. of fuchsin in 100 c.c. of absolute 

 alcohol and 100 c.c. of water. An excellent single stain. Espe- 

 cially to be recommended for preparations that are to be 

 photomicrographed. It stains different tissues different tints 

 of red. 



