PART II. 



THE PREPARATION AND EXAMINATION 

 OF MICROSCOPICAL SPECIMENS. 



The following directions are limited to those of fundamental import- 

 ance which are likely to be employed by students who are beginning their 

 histological studies. Further information may be obtained from "The 

 Microtomist's Vade-mecum" by A. B. Lee (3d ed., 1903, Blakiston, 

 Philadelphia) and from Mallory and Wright's "Pathological Technique" 

 (3d ed., 1904, Sauhders, Philadelphia). The latter is particularly 

 adapted to the needs of medical students. 



FRESH TISSUES. 



Certain transparent tissues may be studied advantageously in a fresh 

 condition. The/ are merely spread in a thin layer upon a clean glass 

 slide, and after a drop of tap water and then a clean cover glass have been 

 placed upon them, they are ready for the microscope. (The glass slides 

 and covers are to be washed with water, using soap if necessary, and 

 sometimes alcohol or strong acids, but all trace of these must be removed. 

 Linen cloths, because of their small quantity of lint, are the proper towels 

 for drying the glassware. Covers and slides as received from the dealers 

 are never ready for use, and some which remain hazy after thorough wash- 

 ing are worthless.) The fresh tissue is spread upon the slide with needles, 

 being 'teased' into small fragments or drawn out into a thin film. Pure 

 water causes some swelling of the tissue so that dilute solutions of common 

 salt are preferable. A 0.6 per cent, solution has recently been found to 

 cause less distortion than the somewhat stronger solutions formerly recom- 

 mended. The tissue having been spread in the center of the slide and a 

 drop or two of salt solution placed upon it, the cover glass is lowered so that 

 air bubbles are not caught beneath it. Especially with the larger slides 

 which are to be preserved permanently this should be done as follows. The 

 square or oblong cover glass is held over the specimen and its left edge is 

 first brought in contact with the slide; a needle held in the left hand 

 keeps this edge in position. Another needle held in the right hand with its 



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