54 Paraffin Method (chap. 5) 



vidual sections to stick to each other. As the ribbon forms, hold it away 

 from the knife with a camel hair brush and ease it forward so that the 

 sections do not remain on the knife. This is advisable to prevent the 

 sections from bimching and piling on each other. They can stack high 

 enough to topple over the edge and get caught between the tissue carrier 

 and the next stroke of the knife. The parallel edges of the paraffin block 

 must be cut clean and parallel. If the edges have not been trimmed, but 

 remain as the original sides formed by the mold, a ribbon will not form. 



In dry weather static frequently becomes a problem during section- 

 ing. The sections stick to the knife or to parts of the microtome. They 

 break apart and stay bunched up instead of lying flat. The friction of 

 the knife as it crosses the paraffin block forms static electricity on its 

 surface. An inexpensive little instrument, the Reco Neutra-Stat,^ may 

 be used to relieve this situation. An alpha radiating static eliminator 

 strip in a slot on the head of the instrument irradiates the air with 

 harmless alpha particles. These ionize the air and discharge static 

 charges from the block surface. 



The ribbons formed during sectioning can be mounted directly on 

 slides, floated on a water bath, or laid in order in a box. The latter is 

 particularly convenient when the slides cannot be made immediately, or 

 when numerous sections have to be cut, serial sections for instance. 

 Hosiery boxes make handy containers, and if painted black inside with 

 India ink, provide an excellent dark background for the sections. If the 

 shorter edges of the block were not trimmed parallel, a serrated edge 

 along the ribbon indicates the exact position of each individual section, 

 minimizing the danger of cutting through one. The sections can be 

 stored in boxes until all required slides have been mounted. Valuable 

 sectioning time is conserved by this means. 



Difficulties Encountered While Sectioning and 

 Suggested Remedies^ 



I. Ribbons are crooked. 



a. Wedge-shaped sections caused by poor trimming; sides of paraffin 

 block are not parallel, or not parallel to edge of knife. 



b. Part of knife edge may be dull; try another part of it. 



c. Uneven hardness of the paraffin; one side may be softer than the 

 other, or contain areas of crystallization. Reimbed. 



' #61-579 Reco Ncutra-Stat, Model M, for microtomes. E. Machlett and Son, 220 E. 23rd 

 Street, New York 10, N.Y., or from Lipshaw Manufacturing Company. 

 "Modified after Richards, 1949. 



