. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . Fig. 2. Thermal advance microtome. the cross-sections varies from 30 to 60 /< for fibres 20 /< in diameter. These cross-sections are swollen in water and swelling is fixed by the zinc chloroiodine reagent. They are dehydrated in alcohol and immersed two days in a first mixture of destabilized methyl methacrylate and butyl methacrylate 50/50. Polymerization is carried out in a second mixture of the same composition in a special cell which allows the orientation of the cross- sections (3, 10, II 12). A perspe
. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . Fig. 2. Thermal advance microtome. the cross-sections varies from 30 to 60 /< for fibres 20 /< in diameter. These cross-sections are swollen in water and swelling is fixed by the zinc chloroiodine reagent. They are dehydrated in alcohol and immersed two days in a first mixture of destabilized methyl methacrylate and butyl methacrylate 50/50. Polymerization is carried out in a second mixture of the same composition in a special cell which allows the orientation of the cross- sections (3, 10, II 12). A perspex tube, 10 mm long, containing the monomer and the cross-sections is mounted between the two electrodes of the cell (fig. 1). A 50 cycles alternative current of 3 to 4 KV is applied between the electrodes. The whole cell is rocked one cycle per second with an 180 angle. There cannot be any decantation of the cross-sections towards the bottom of the perspex tube. Rocking insures good dispersion of these cross-sections into the embedding medium. Under the elTect of the electric field, the fibre sections are oriented while the polymerization takes place at 40"C for 6 hours. Cross sectioning on a thermal advance microtome.— After polymerization is completed, we have at our dispo- sal a cylindrical perspex block in which all cross-sections are oriented parallel to the cylinder axis. This block is cut with a thermal advance microtome (fig. 2) (2, 5). The cross-sections are cut again in a much thinner section (100 to 300 A thick). A small brass container (7, 8) is fixed with the help of paraffin to a glass knife (13). The brass container is connected to a glass tube by rubber tubing. By these means the level of the liquid (water-acetone mixture) is ajusted correctly. The ribbon of sections is picked up on formvar film coated grids. Fig. 3 shows a result obtained when the embedding medium has not been removed. Contrast in this micro- Fig. 1. Perspex cell for the embedding of sec
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