. The microscope; an introduction to microscopic methods and to histology. Microscopes. 184 PARAFFIN SECTIONING [CH. VII for each method. The time might be longer or shorter than for the picric-alcohol. (See Lee, the Microtomists' Vade-Mecum.) If picric-alcohol is used, pour it off after the proper time for fixing has elapsed, and add (>"]% alcohol. Leave this on the tissue from one to three days, and if it becomes ver}' yellow it is well to change it two or three times. After two or three days pour off the 67%' alcohol and add 82%. The tissue should remain in this one or two days, and
. The microscope; an introduction to microscopic methods and to histology. Microscopes. 184 PARAFFIN SECTIONING [CH. VII for each method. The time might be longer or shorter than for the picric-alcohol. (See Lee, the Microtomists' Vade-Mecum.) If picric-alcohol is used, pour it off after the proper time for fixing has elapsed, and add (>"]% alcohol. Leave this on the tissue from one to three days, and if it becomes ver}' yellow it is well to change it two or three times. After two or three days pour off the 67%' alcohol and add 82%. The tissue should remain in this one or two days, and it may remain indefinitely. In case the alcohol becomes much yellowed, it should be changed. <s 2S5. Dehydration and Preparation for Imbedding,—From the pieces of tissue fixed and hardened in any approved manner, cut pieces 5 to 10 millimeters long and 2 to 3 millimeters in breadth. Place one or two pieces in a shell vial (Fig. 143.) and add 95",, alcohol. Change the alcohol after two or three hours, and within 6 to 24 hours, depending on the size of the piece to be dehydrated, the dehydration will be completed. The secret of success is the use of plenty of alcohol and sufficient time. Absolute alcohol for the second change would act more promptly and efficiently, but if plenty of 95",, is used one will succeed, unless the day, or the climate in general, is too Fig. 154, Copper pail with water bottom for melting para- ffin. This also series as a water bath for large bottles in which saturated solutions of diehro- mate and other salts are pre- pared. (If one is studying organs, then the whole organ may need to be prepared for imbedding, but for minute structure small pieces are preferable, as thinner sections may be made.) (S 2S6. Displacing Alcohol and Clearing Tissues with Cedar-wood Oil and Infiltrating with Paraffin.—(Lee, p. 66. Keelson and Schiefferdecker, Arch, fur Anat. und Physiol., 1882, p. 206.) When the tissue is dehydrated it is removed to a
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