190 



PARAFFIN SECTIONING 



\CH. VII 



\ 296. Counterstaining with Picro-fuchsin. —For a general dye to use with 

 hematoxylin, eosin is good, but to differentiate the tissues more completely, 

 especially connective tissue, which is present in practically every section made, it 

 is better to use Van Gieson's mixture of picric acid and acid fuchsin. (Picric 

 acid, saturated aqueous solution 75 cc, water 25 cc. 1% aqueous solution of acid 

 fuchsin, 10 cc.) Sections are first strongly stained with hematoxylin, well washed 

 with water and then stained 3 seconds to 15 minutes in the picro-fuchsin. They 

 are then washed in distilled water ; or in tap water, to which has been added a drop 

 or two of glacial acetic acid to 100 cc. of water. They are then dehydrated, 

 cleared and mounted in acid balsam, that is in balsam which has not been neutral- 

 ized ($ 315). If glycerin or glycerin jelly is used as a mounting medium it should 

 be slightly acid. Unless the mounting medium is slightly acid, the red of the 

 acid fuchsin soon fades. In some cases less acid fuchsin should be used, and in 

 some a greater amount. Acid fuchsin alone without the picric acid is also good 

 for a counterstain. The picro-fuchsin is a very valuable differential stain and 

 combined in different proportions with picric acid will give great assistance in al- 

 most every case. It does not seem to be a permanent stain. (See Freeborn, 

 Trans. N. Y. Path, Soc, 1S93, p. 73. Also studies from the department of pathol- 

 ogy of the College of Physicians and Surgeons, Columbia University, N. Y., 

 1 894- 1 895). 



161. Copliu's staining dish. A. The 

 entire dish; B. the dish in cross section. 

 This is made of glass and is a very neat piece 

 of apparatus. With it ten slides may be 

 stained at once. ( Whitall, Tatum & Co. ) 



\ 297. Dehydration of the Stained Sec- 

 tions. — Place the slide with the stained sec- 

 dons in a jar of 95% or absolute alcohol and 

 save it a few minutes, or wave it around in 

 the alcohol for half a minute or so. 



Remember that the larger and thicker 



the sections the more time it requires to de- 



cross-section hydrate them. In a moist atmosphere, 95% 



SHOWING SLIDES / . ^ y0/0 



in position. alcohol is not completely satistactory, and 

 one must use a stronger alcohol. When it is dry, 95% answers very well. 



\ 298. Clearing the Sections. — Drain off the alcohol, and place the slide in a 

 jar of clearer (§ 318, A or B) or put a drop or two of clearer on the sections. The 

 clearing is usually accomplished in two or three minutes. 



\ 299. Mounting in Balsam. — For this the clearer is drained from the 

 slide, and wiped away with blotting paper, cloth, etc. The balsam is then put 

 upon the sections and the cover added, or a cover-glass is spread with the balsam 

 and then put over the sections. ( If the sections show a whitish appearance and 

 are opaque they were not sufficiently dehydrated. If natural balsam is used the 

 sections will clear up in time). 



