I] MICROSCOPIC EXAMINATION 19 



either Williams's or Cathcart's microtome, and above all for 

 Ijardened materials, the Cambridge rocker. By this latter 

 the most exquisite and uniformly thin sections in a riband 

 are obtained. 



As regards hardened material, it is necessary to remember 

 that the hardening must be carried out properly, small bits 

 — about a half to one cubic inch — of tissue being placed in 

 alcohol, or better, in Miiller's fluid, and kept there ; in the 

 first instance, for two to five days ; in the second for from 

 one to three weeks or more. Then small bits are cut out, 

 of which it is desired to make sections. Those hardened 

 in spirit must be soaked well in water to enable the material 

 to freeze, then superficially dried with blotting-paper, and 

 then used for cutting sections with the microtome. Those 

 hardened in Miiller's fluid are at once superficially dried 

 with blotting-paper and cut. When making sections with 

 Williams's freezing microtome it is necessary to soak the 

 material first in gum mucilage and then to freeze and to cut. 

 Fresh tissues are at once cut with the freezing microtome, 

 the sections placed in a o-6 per cent, saline solution, floated 

 out and well spread out, and then stained by transferring 

 them in this condition — i.e., well spread out, into a watch- 

 glass containing the dye. The sections of hardened tissues 

 are floated out in water, well spread out, and then trans- 

 ferred to the dye or dyes as the case may be. 



It is necessary to prevent too much shrinking of the 

 sections, especially those of fresh tissues ; for this reason it 

 is advisable to float the sections in the saHne solution or 

 water, as the case may be, on a broad lifter or spatula, to 

 spread them well out upon it, and to transfer them carefully 

 into the dye, then into the dish with water used for washing 

 off the excess of the dye, to transfer them, well spread out 

 on the lifter, to alcohol, then after several minutes to oil of 



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