88 A MANUAL OF BACTERIOLOGY 



The xylol dissolves out the infiltrated paraffin, and 

 the sections are then placed in alcohol to extract 

 the xylol. After this treatment they are ready for 

 the staining process. 



Instead of celloidin and paraffin, wax-and-oil 

 mixture l and vaseline-and-paraffin mixture are used 

 for imbedding purposes. 



Before alcohol-hardened tissues are cut with the 

 freezing microtomes they must be soaked in water 

 for ten minutes, this process to be followed by five 

 hours' soakage in mucilage. After this they are 

 frozen and cut with the microtome, whose razor 

 must be perfectly sharp and free from notches. 

 Tissues hardened in Muller's fluid (if they have not 

 been subsequently placed in alcohol) are at once 

 dried with blotting-paper, then frozen, and finally 

 cut. Fresh tissues are covered with mucilage, 

 frozen, and cut. The razor should be moistened 

 with a solution of gum, and the sections transferred 

 with a camel-hair brush to warm distilled water for 

 fifteen minutes the object being to dissolve out the 

 mucilage. They are then ready for staining, etc., 

 with the exception of sections of fresh tissues, which 

 should be placed, before staining, in a 0'6 per cent, 

 saline solution, so as to prevent too much shrinking 

 of the sections. 



In cutting sections with the microtome ' very 

 little force is required in pushing the razor or knife 

 through the material, and if it is sharp a very slight 

 turn of the screw each time will enable one to cut a 



1 Equal parts (by weight) of white wax and olive oil are 

 melted together. 



