INDUSTRIAL RESEARCH 



excite fluorescence in the specimen. Normal from artifact by the establishment of this 



optics may be used in most appHcations; relationship. Interpretation is thereby facili- 



however, sometimes it is desiral)lc to utilize tated when structure is ultimately seen at 



the shorter wavelengths which are absorbed the same and higher magnifications from the 



by glass. Then it is necessary to substitute perspective of the image produced by elec- 



quartz or reflecting optic components plus trons rather than by light, 



first -surf ace aluminum mirrors in the il- Further discussion of the crossing of dis- 



luminating system. Even the microscope ciplines could lead to an inappropriately 



slide should be made of quartz. Most often lengthy section. These examples have been 



an adequate illuminating system for fluores- cited here, not only because of their indi- 



cence studies can be set up by employing a vidual value, but also because they ser^'c to 



mercury arc lamp with an appropriate filter exemplify an effective approach in micro- 



as a source, together with a dark-field con- scopical research. 



denser. Only the fluorescent light from the Specimen Preparation. It must be 

 specimen and small amounts of scattered emphasized that specimen preparation is one 

 radiation are thereby permitted to enter the of the most important aspects of micro- 

 objective. If bright-field illumination were scopical research, and therefore, deserves 

 used, the undeviated beam entering the ob- considerable attention. Fine structure on 

 jective would be highly objectionable from one scale or another is present in almost any 

 the standpoint of harm to the eye as well as object. When the order of magnitude of 

 of exciting fluorescence in the cement of the some detail or inhomogeneity of that struc- 

 objective lens. ture falls within the resolving range of the 



Not always is it necessary to excite with microscope, such material is amenable to 



ultraviolet light. In some cases, visible light study by the techniques outlined above, 



which is shorter than that of the anticipated However, without some prior treatment, the 



fluorescence may provide the excitation. object does not usually exhibit the detail 



Combining Light and Electron Microscopy, required for exhaustive examination. The 

 Light and electron microscopy can and treatment given a sample to create a speci- 

 should be used in combination. Ordinarily men appropriate for microscopj^ is construed 

 it is inadvisable to proceed directly to elec- here as specimen preparation, 

 tron microscopy without first having done Ordinarily specimen preparative methods 

 light microscopy. This statement is con- are performed to confine observation and to 

 sistent with the recommendation that a reveal structure in the chemical and phj-sical 

 microscopical study should be initiated at sense, both specific with regard to certain 

 lower magnifications than that of which the constituents, and nonspecific. In order to 

 electron microscope is capable. It finds delineate suflficient detail for interpretation 

 further justification in the narrowly limited of the morphology, it is often possible to 

 nature of electron-microscope specimens, use nonspecific preparations. These most 

 Obviously, the sampling problem in electron frequently include treatments which modify 

 microscopy is more acute, in view of the the optical properties of the sample. How- 

 required smaller specimen size. Furthermore, ever, they may not entail changing the 

 a suitable specimen preparation for electron sample, but rather defining certain features 

 microscopy is likely to exhibit structure in of the sample for microscopical viewing. An 

 an unrecognizable form unless the transition example of the latter is surface replication of 

 in the rendition of structural detail is related an untreated sample, and of the former, the 

 first by light microscopy. Very often much reduction of optically confusing surface 

 of the true structure can be distinguished roughness by polishing. These general 



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