180 COLLODION SECTIONING \CH. VII 



\ 278. Staining the Sections with an Alcoholic Stain. — If an alcoholic 

 stain containing 50% or more alcohol (for example, hydrochloric acid carmine in 

 70% alcohol) is used, the slide may be removed from the 95% alcohol, drained 

 somewhat and then the stain poured upon the sections, or preferably, the slide 

 immersed in a jar of the stain. The stain is finally washed away with 67% or 

 stronger alcohol, the sections dehydrated in 95% alcohol, cleared and mounted in 

 balsam. 



I 279. Staining the Sections with an Aqueous Dye. — In staining with a 

 watery stain, the slide bearing the sections is transferred from the 95% alcohol 

 and plunged into a jar of water, and either allowed to remain a few minutes or 

 moved around in the water a moment. Then it is placed horizontally and some 

 of the stain placed on the sections with a pipette, or preferably, it is immersed in 

 a jar of the stain ; in case of immersion the slide should stand vertically or nearly 

 so, then any particles of dust, etc., in the stain will settle to the bottom of the 

 vessel and not settle on the sections. When the sections are stained, usually 

 within five minutes, they are thoroughly washed with water either by the use of a 

 pipette or preferably by immersing in a jar of water. They may then be counter- 

 stained for half a minute with some general dye, like eosin or picric acid, or 

 mounted with but the one stain, j 



^Various forms of paper have been used to handle the collodion sections. It 

 should be moderately strong, fine meshed and not liable to shed lint, and fairly 

 absorbent. One of the first and most successful papers recommended is "closet or 

 toilet paper. " Cigarette paper is also excellent. In my own work the heavy white 

 tissue paper has been found almost perfect for the purpose. Ordinary lens paper 

 or thin blotting paper for absorbing the oil may be used with it. ($ 275). 



tlf one is a long time in cutting a series of sections, it sometimes occurs that 

 the xylene evaporates, and while the sections may not look dry, they are practically 

 in castor oil and not easily transferable. In such a case fresh clarifier or even a 

 little xylene to thin the oil on the sections may be used. If the oil is too thick it 

 is viscid and there is difficulty in handling the sections with the paper as they 

 stick rather firmly to the knife. (§275). 



fin the past the plan for changing sections from 95% alcohol to water, for ex- 

 ample, has been to run them down gradually, using 75, 50 and 35% alcohol, suc- 

 cessive!}'. Each percentage may vary, but the principle of a gradual passing from 

 strong alcohol to water was advocated. On the other hand I have found that the 

 safest method is to plunge the slide directly into water from the 95% alcohol. The 

 diffusion currents are almost or quite avoided in this way. There is no time for 

 the alcohol and water to mix, the alcohol is washed away almost instantly by the 

 flood of water. So in dehydrating after the use of watery stains, the slide is 

 plunged quickly into a jar of 95% alcohol. The diffusion currents are avoided in 

 the same way, for the water is removed by the flood of alcohol. This plan has 

 been submitted to the severe test of laboratory work, and has proved itself perfectly 

 satisfactory. 



