STAINS, ETC. 



1380 



FIXATIVES 



benzol, toluol, chloroform, or turpentine. Filter 

 through paper and keep in a " capped " bottle. If it 

 gets too thick, dilute by adding more of the solvent 

 employed. Colophonium. A solution in turpentine 

 is recommended by Kleinenberg. This medium sets 

 very slowly, and so affords ample time for arranging 

 objects in it. Alcohol must not be used as a solvent, as 

 in time it throws down a precipitate. Dammar. The 

 menstrua are the same as for Canada balsam, and the 

 solutions are prepared in the same way. A solution in 

 a mixture of benzol and turpentine is recommended by 

 Flemming and Pfitzner. Oil of Cedar. This medium 

 soon sets hard enough to hold the cover in place, and 

 so obviates the necessity of sealing the mount, except 

 for immersion-work. See Clearing Agents . Seller's 

 Alcohol Balsam. Evaporate Canadabalsam todryness 

 in a water-bath ; dissolve while warm in warm absolute 

 alcohol, and filter through absorbent cotton. Venice 

 Turpentine. Vosseler recommends this medium as 

 possessing certain advantages over Canada balsam and 

 dammar. The turpentine is mixed with an equal 

 volume of 96 per cent, alcohol, allowed to stand in a 

 warm place for three weeks, and then decanted. Sec- 

 tions may be mounted in this medium without previous 

 clearing in an essential oil, and it is said that stains 

 are permanent in it. Its index of refraction being 

 lower than that of the media already named, it gives 

 better definition to the delicate details. Xylol-bal- 

 sam. See Canada Balsam. 



FIXATIVES. 

 To facilitate the staining and mounting of sections, 

 various preparations are used to cause them to adhere 

 to the slide. The following include the more import- 

 ant fixatives and methods of procedure. I. Aqueous 

 Sections. Fol's Gelatin Method. Dissolve 4 

 gm. of gelatin in 20 c.c. of glacial acetic acid by 

 means of the water-bath and agitation. Add to 5 

 c.c. of this solution 70 c.c. of 70 per cent, alcohol 

 and 1 to 2 c.c. of 5 per cent, aqueous solution of 

 chrome-alum. Pour this preparation on the slide and 

 allow it to dry. Immerse the slide in water contain- 

 ing the sections, arrange them on it, and remove it. 

 This method is applicable to sections made under 

 water. II. Celloidin Sections. Apathy's Oil 

 of Bergamot Method. Cut the sections with a 

 knife anointed with vaselin and wetted with 95 per 

 cent, alcohol and float them on bergamot-oil. Before 

 they sink, push each one, by means of a needle, into 

 place on a piece of tracing paper dipped in the oil. 

 When the desired number are in position, the paper is 

 drained, dried on the under side with blotting-paper, 

 turned over, and gently pressed down on the slide. 

 Remove the paper by rolling it up from one end ; the 

 sections remain adherent to the slide. The remain- 

 ing bergamot-oil may be removed by cigaret-paper. 

 Apathy's Series -on- the- Knife Method. The 

 knife is evenly rubbed with yellow vaselin and moist- 

 ened with 70 to 90 per cent, alcohol. The sections 

 as they are cut, are drawn with a needle to a dry 

 part of the blade, and arranged in rows, so that the 

 celloidin of one section overlaps that of the next. 

 When a series has been completed, the sections are 

 dried by laying blotting-paper upon them and then 

 painted over with the thickest celloidin solution used 

 for embedding. This is allowed to evaporate for five 

 minutes in air, and then wetted with 70 per cent, alcohol, 

 which hardens the celloidin into a continuous lamella 

 which can be readily detached by means of a scalpel. 

 Pregl's Acetone-celloidin Method (Sternberg). 

 When not embedded in paraffin, the sections, com- 

 pletely dehydrated, are taken out of absolute alcohol 



on a thin cover-glass, upon which they are extended: 

 a piece of filter-paper is applied to the side of th< 

 cover-glass to absorb the alcohol, and before the sec 

 tion is completely dry a drop of acetone-celloidin is 

 placed upon it by means of a glass rod. The cover 

 glass is now moved about in the air to promote rapic 

 evaporation of the alcohol, and then placed in water 

 The sections remain attached to it. The acetone-eel 

 loidin solution is prepared by adding celloidin ir 

 small, dry pieces to acetone until a concentrated solu 

 tion is obtained. A large drop of this added to 1 

 c.c. of absolute alcohol makes a suitable solution fo 

 use. This must be kept in a glass-stoppered bottle 

 and be frequently renewed, as it absorbs moistun 

 from the air. The acetone obtained from dealers mus 

 be dehydrated by adding red-hot copper sulphate 

 Summers' Ether Method. After placing the sec 

 tions in 95 per cent, alcohol for a minute or two, ai 

 range them on the slide and pour over them ethej 

 vapor from a bottle partly full of liquid ether. Thi; 

 softens the celloidin and makes it perfectly transpai 

 ent. The slide may now be placed in 95 per cen i 

 alcohol, and the sections will be firmly fixed to i I 

 Weigert's Method. This method consists inholdin 

 the series between two adherent films of cellokiirj 

 A glass plate of sufficient size to accommodate tl j 

 sections, cleansed with ether and alcohol, is coatej 

 with a thin film of celloidin and left to dry. Tl 

 sections, as they are cut, are taken off on a strip i 

 tissue-paper which has been laid upon a piece of bk| 

 ting paper wet with 80 per cent, alcohol. When tl! 

 series is complete the tissue-paper is lifted and tunic, 

 section-side down, on the celloidin film on the gla 

 plate; the tissue-paper is then removed, and any r 

 maining alcohol absorbed with bibulous paper. A 

 other film of celloidin is then poured over the sectioi 

 and after a short exposure to the air, the plate is ill 

 mersed in water, section-side up. In a short time t 

 film enclosing the sections will become detached a 

 float to the surface. Remove it on tissue paper, an 

 stain, either whole or in parts, in the usual way. T 

 plate, with the adherent films, may, if desired, be pi I 

 served in 80 per cent, alcohol. III. Paraffin SbI 

 tions. Flogel's Gum Method. To a filter. 

 tion of I part of gum arabic in 20 parts of water, ad(' 

 little alcohol to prevent mold. Pour this preparati 

 over perfectly clean slides, and drain. Secti 

 mm. in thickness may be placed on the wet gum > 

 face and floated to the proper position — a good metru \ 

 when the slide is not subsequently treated with aqu« 

 solutions. Frenzel's Gum Method. To a thin n 

 cilage of gum arabic dissolved in water add an aquet 

 solution of chrome-alum, and then a little glycerin tl 

 a trace of alcohol. Put a little of the preparation i 

 the slide, place the sections in position, and heat ] 

 15 minutes at a temperature of 30 to 45 C. wh ■ 

 renders the gum insoluble. This gum has the 

 vantage of not reacting to the majority of stain 

 fluids. Safranin and fuchsin should be avoid ■ 

 Gaule's Methods. Moisten the slides with watei 

 dilute alcohol, place the sections in position, 

 move the surplus fluid by means of bibulous pa] 

 and dry in a thermostat at 50 C. for 24 hot 

 Sections so treated are then heated for a mora 

 above the melting-point of paraffin, which fix< 

 securely to the slide. Gaule's xylol method isi 

 follows : Place the sections on a slide moistei 

 alcohol; warm slightly, cover, and run undei 

 ture of equal parts of Canada balsam and xylol. • 

 refill the cell daily as the xylol evaporates, and 

 plete with xylol-balsam. Mayer's Albumen Meth 

 Mix equal volumes of fresh filtered white of > 



