The Use of Carbon Films to Support Tissue Sections for Electron Microscopy

Since the earliest days of electron microscopy one of the most irksome technical problems has been that of specimen drift. With the application of high-resolution microscopy to thin sections of biological material this problem has become even more acute. Sections mounted on collodion or formvar-coated grids show a persistent tendency to drift which may be minimized by reducing the thickness of the sections as much as possible, by relatively long exposure to vacuum, and by stabilization with the electron beam, The last mentioned procedure is rather effective but is also destructive in that it reduces contrast considerably by adding a layer of comtaminafion. Finally, exposure to the electron beam usually results in shrinkage of formvaror collodionsupported sections amounting to perhaps 10 per cent in one dimension. This may serve to enlarge preferentially, those spaces between tissue-laden areas, as between membranes, thus introducing a complex, small-scale distortion of fine structure. In order to minimize sublimation of the embedding material, low beam intensities were used by Sjfstrand (1) and by Rhodin (2) to produce excellent micrographs. While such a procedure appears to be effective, it is inconvenient because of the difficulty at low intensities of scanning for suitable areas and of focusing. The use of carbon films as support for