_Logwood or Hæmatoxylin Stains_ (see Appendix for the several formulæ). Staining by this agent is effected as follows:--
After the specimen has been hardened in any of the chromic acid solutions in use, transfer it to a seven per cent. watery solution of bicarbonate of soda for about five minutes, then wash well in distilled water. Spirit prepared preparations do not require to be transferred to the soda solution, but all sections must be washed before they are transferred to the logwood stain. To a watch glass nearly full of distilled water add ten or twenty drops of the logwood stain, in which it should remain for twenty or thirty minutes. Wash well with the ordinary tap water, which will fix the dye and cause it to become blue. Dehydrate in methylated spirit, clear in clove oil, and mount in dammar or Canada balsam.
_Double-staining with Hæmatoxylin and Rosin._--Stain the section as directed above, then place it in an alcoholic solution of rosin, about one gramme of rosin to an ounce of methylated spirit, and let it soak for a few minutes; wash well in methylated spirit, clear in oil of cloves, and mount in balsam.
_Canada balsam_ should be prepared for use as follows:--One ounce of dried balsam to one fluid ounce of pure benzole; dissolve, and keep in an _outside_ stoppered bottle. Clear the section in clove oil, and place it in turpentine, clean a cover-glass and slide, place a few drops of balsam on the centre of the latter, take the section from the turpentine on a _lifter_, allow the excess of turpentine to drain away, and with a needle-point lift the section on to the balsam slide. Now take up the cover-glass with a pair of forceps (Fig. 236), and bring its edge in contact with the balsam, ease it down carefully as shown in Fig. 237, so that no air bubbles are enclosed, and with the needle point press the surface of the cover until the section lies quite smoothly and flat, and the excess of balsam is pressed out. The slide should now be transferred to the _warm-chamber_, and there allowed to remain for a day or two, or until set and hardened.
[Illustration: Fig. 236.--Forceps for Mounting.]
Any exuded balsam may be washed away with benzole and a soft camel’s hair brush; then dry the slide with an old piece of linen cloth, and apply a ring of cement or Japanner’s gold size. Other methods for staining and mounting will be found to answer quite as well--that of Beneke’s is a useful one for staining connective tissue.