Abstract
From the theoretical and experimental view points the author has improved the method for freezing-drying and succeeded in establishing a method suitable for the electron microscopy by which the frozen-dried cells show their detailed fine structures under electron microscope without staining or using any fixative. The method is as follows: a piece of fresh tissue smaller than 0.5 mm3 in size is frozen promptly in liquid propane, cooled at about -180°C by liquid nitrogen, and dried at -60°C for 60 hours with the vapor trap of liquid nitrogen set at as short distance as less than 0.5 cm. and in vacuum of less than 10-4 mm. Hg. After 60 hours the temperature is raised gradually to the room temperature during the subsequent 15 hours The tissue is dipped in methacrylate without breaking vacuum and embedded by polymerizing with benzol-peroxide at 40°C for 12 hours. Thin sections can be obtained and observed under electron microscope without staining or affecting with any fixative. Successive photographs of pancreatic exocrine cells are seen in the last two figures.
