The Complementary Nature of Light and Electron Microscopy

SYNOPSIS Some aspects of recent progress in microscopy are reviewed. The widespread development of histology at the electron microscope level has been made possible by technical advances such as the design of microtomes capable of cutting very thin sections, the development of suitable methods of fixation and embedding, and the invention of the glass knife. Some basic principles of microscopy are discussed and the origin of contrast is considered. It is shown that in many cases microscopic methods reveal the distribution of mass per unit area. This mass may be specific, as in the case of certain staining or absorption methods, or non‐specific, (i.e. total) as in the case of refractile objects and in electron microscopy. It is emphasized that no single method is capable of revealing all the physical and chemical properties of a specimen, and an examination under the microscope must be regarded as one of many possible experiments.