28 MICROSCOPICAL RESEARCH 



position for cutting, with hot needles, and as soon as the 

 "block," or mould, is just set on the upper surface plunge the 

 entire mould into cold water; by this means the block will be 

 cooled uniformly. If this operation be carried out successfully 

 the block, when removed from the mould, will appear 

 uniformly transparent. Should this not be the case one of 

 \ three things will have taken place : — 



( 1 ) The specimen has not been properly dehydrated ; 



(2) The chloroform has not been completely evaporated ; 



(3) The block may have been cooled too slowly. 



Either defect will be indicated by a milky opacity in the 

 centre of the block surrounding the specimen; the only 

 remedy is to re-melt the paraffin and re-mould. 



7. The block containing the specimen should now be trimmed 

 into a square; warm the paraffin in the orientator, or carrier 

 of the microtome, and also the base of the block containing 

 the specimen, press them gently together; then seal the joint 

 with a hot needle, and the preparation is ready for sectionizing. 

 After the sections are cut they may be fastened to the slide 

 with Mayer's albumen solution. 



Foi-mula. 



White of egg, 50 cc. "1 



Pure glycerine, 50 cc. [ Shake well to dissolve. Filter for use 



Salycilate of soda, i grain 



J 



