Electron Microscopy 403 



Pease {I960) makes the following suggestions: make solution 

 changes, fixation, dehydration, etc. in small wide-moiithed weighing 

 bottles. He considers the blocks formed by pure butyl methacrylate 

 as too soft and adds anywhere from 10 to 30% of ethyl methacrylate 

 to his soliuion. The catalyst dissolves slowly and must be complete 

 before the solution is placed in the capsules. He recommends poly- 

 merization by ultraviolet light, saying that it forms a block superior 

 to that formed by heat. It is more iniiform and has fewer btibbles. 

 Use a Westinghouse Fluorescent Sun Lamp bulb, :fp5TT12 about 1 

 inch from the capsules. 



Ultrathin Sectioning 



Conventional-type microtomes have been modified for ultrathin sec- 

 tions. Pease and Baker (1948); Newman, Borysko and Swerdlow (1949); 

 Newman (1930); Gere?! and McCullock (1951); Nylen and Holland 

 (1957). Three good specially designed microtomes are available: 



1. Porter and Blum (1953) utilizes a cantilever action, is manufactured 

 and distributed by Ivan Sorvall, Inc., Norwalk, Conn. 



2. Sjostrand utilizes a thermal expansion feed and is motor driven, is 

 manufactured by LKB Produkter in Stockholm, is handled by Sor- 

 vall. 



3. Reichert of Austria also manufactures one. 



KNIVES 



Steel knives must be exceedingly sharp, but are dulled rapidly by 

 plastic cutting. 



Glass knives are popular and cheap. They can be made from 3/16 

 inch or ^ inch plate glass, shaped as rhomboidal equilateral parallelo- 

 grams with a cutting edge of 45° (Porter and Blum, 1953), and fitted 

 in a specially designed holder (Cameron, 1956 and Sheldon, 1957). 

 They dull rapidly btu are easily replaceable; they can be made in the 

 laboratory or purchased from Acme Glass Company, Cambridge, Mas- 

 sachusetts. Gavin and Lloyd (1959) recommend a vycor brand glass 

 for less scratching in the sections. The angle between front side of 

 the knife and the plane of the passing section shotild not exceed 10°, 

 preferably 3-50. Sjostrand uses a hand-sharpened Schick razor blade 

 in a special holder. 



Diamond knives (Fernandez-Moran, 1953, 1956; Crandall, 1961) 

 are more durable biu are expensive. Sorvall carries them. 



