Method I 17 



boxes placed upon the paraffin bath. Arrange the pieces in 

 position for sectioning and 



(d?) Cool quickly by transferring the receptacle to ice water. 



Rapid cooling prevents crystallization, and gives much more 

 solid and satisfactory paraffin blocks than often result from slow 

 cooling. 



Note. — Paper boxes are preferable to other means of imbedding in that 

 (i) they can be cooled more quickly ; (2) they can be made in any shape and 

 size required ; (3) they can be labeled readily ; and (4) they can be stored 

 easily. The paper should be thin and tough, and of a quality which does not 

 shed lint. Ordinary thin linen writing paper is excellent. Make the boxes 

 over the end of blocks of the required size and label them in pencil before 

 removing them from the molding block. When paper boxes are used, the 

 depression in the middle of the paraffin resulting from its contraction on cool- 

 ing may be prevented by lightly pressing the upper edges of the box together 

 as the cooling begins. Imbedded in paraffin the tissue will keep indefinitely. 



5. To section. — [a) Remove the paper from the block of 

 paraffin Containing the piece of tissue required and mount the 

 block firmly on a warmed object-carrier of the microtome, tak- 

 ing care that the imbedded specimen is so .oriented that sections 

 may be obtained in the required plane. Cool quickly. 



(5) Trim the block down to the required size, keeping the 

 edges parallel. The sections will ribbon much better if the 

 block is rectangular, or at least has two of its edges parallel, and 

 is so arranged on the microtome that these edges strike parallel 

 to the edge of the microtome knife. 



(c) Make sections 4-10 micra thick. The ribbons are laid out 

 on a sheet of clean dry paper and there, with a sharp scalpel, 

 cut up into lengths containing the number of sections required 

 for mounting. 



6. Fasten sections on a thoroughly cleaned slide (see general 

 dSxe.c'ixo-a.s 'i,,'^.\2)\i^ t\i& albumen water method. This method 

 is as follows: A very thin film of Meyer's albumen fixative (F) 

 is rubbed onto the slide with a clean finger, and a few drops of 

 distilled water are run over the film. Then lay the slide level 

 and place the sections in position on the slide. Floating on the 

 water, they may now be made to straighten out by gently 



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