'•{OG Special Procedures III (chap. 24) 



sue sections produce an image on photographic emulsion. After photo- 

 graphic processing, the emulsion can be studied by conventional light 

 microscopic methods, and a comparison and correlation made with 

 stained sections. 



Only a brief sinnmary of methods will be discussed and some refer- 

 ences included. All kinds of material can be used. Sections of large bone 

 can be exposed to roentgen-ray film; sections on slides, smeared and 

 squashed material, can be exposed to a covering of stripping or fluid 

 emulsion and tissue cultures can be placed against an emulsion to make 

 an exposure. 



As to fixation, formalin usually is satisfactory, but solutions contain- 

 ing mercuric chloride should be avoided; they produce artifacts on the 

 emulsion (Kaminski, 1955). Solubilities of isotopes must be checked 

 carefully; some leach out in water or paraffin solvents and must be pre- 

 pared by freeze-drying methods [Holt and Warren, 1953). In some cases 

 carbowax can be used, but it will dissolve water-soluble isotopes {Holt 

 et al., 1949, 1952; Holt and Warren, 1950, 1953). Mounting must be 

 handled with care to prevent leaching (Gallimore et al., 1954). 



Witten and Holmstrom {1953) freeze the tissue at the microtome iin- 

 mediately after excision. The knife is kept cold with dry ice, keeping 

 the section frozen after it is cut. Then the section is carried still frozen 

 to the photographic emulsion. As the section thaws it produces a bit of 

 moisture and thereby adheres to the emulsion. 



Bone must not be decalcified for this process. Some of the best tech- 

 nics for bone use methacrylate or epoxy embedding before sectioning. 

 {Arnold and Jee, 1954A, 1954B; Norris and Jerikins, 1960; and Wood- 

 ruff and Norris, 1955) 



There are various methods of assuring contact between specimen and 

 emulsion. 



procedure: 



1. The specimen or slide bearing a specimen can be placed directly 

 on the emulsion, or it may first be protected by a layer of 1% cel- 

 loidin in amyl acetate and then be placed on the emulsion {Holt 

 and Warren, 1950). 



2. Sections can be mounted directly on the emulsion on a slide. 



{a) "Stripping film" method: 



"Stripping film" emulsion is removed from its glass plate. First the 

 edges of the emulsion are cut with a razor blade and the emulsion 

 can be peeled off and floated on distilled water with \% Dupanol 

 (wetting agent) added. Then the slide with the section uppermost is 



