Method XIV 85 



The sections now appear brownish gray. 



6. Rinse well in distilled water (3-5 minutes) and transfer to 

 a covered vessel containing 20-30 volumes of the chromogen solu- 

 tion ( D-, I ) for 2-6 days. 



Change the fluid after the first 12 hours. 



7. Replace chromogen solution (D, i) with iG-20 volumes 

 of the pure chromogen solution (D, 2) for 12-48 hours. 



8. To stain. — Merely rinse the sections (1-2 minutes) in dis- 

 tilled water, withdraw the water, and pour over them, in a well- 

 covered shallow dish, 10-20 volumes of the methyl violet-oxalic 

 acid solution (E), and let the stain act for J^-2 hours. 



9. To differentiate. — («) Rinse the sections, one at a time, 

 quickly (about i second) in physiological salt solution (F). To 

 do this, have the salt solution in a shallow dish ; with a needle 

 hold the section by its celloidin margin on a section lifter, or 

 spatula, and simply dip it through the salt solution two or three 

 times. 



Then, still holding it, transfer it immediately to Lugol's solu- 

 tion (G) for 2-8 seconds. 



Finally plunge it into a vessel containing a copious amount of 

 distilled water. Here it may remain for 10-15 minutes. The 

 sections are now a brownish black. 



The time the section should remain in the Lugol's solution 

 (iodine) can be ascertained only by experiment. The time 

 required varies for different specimens of tissue. Complete a 

 few sections at a time, and examine them before removing others 

 from the stain. 



(^) From the water the sections must be dried with filter 

 paper. Place the sections, two or three at a time if desired, on a 

 slide, place over them a piece of thin porous tissue paper, and 

 over this several thicknesses of filter paper. With an ironing 

 motion, press the filter paper down, changing its position till the 

 part over the sections ceases to become moist. This not only 

 dries the sections, but irons them" out flat. 



{c) Carefully remove the paper, and the sections will be left 

 sticking to the slide. Then with fine pointed forceps grasp a 



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