Hot knife microtomy for large area sectioning and combined light and electron microscopy in neuroanatomy and neuropathology.

The technical details given in this paper meet the demand in neuroanatomy and neuropathology for methods which combine broad light microscopical surveys with detailed ultrastructural studies of logically selected areas in well perfused brain material, and emerge directly from experiences in Palay's laboratory at the National Institutes of Health in 1956. Using the procedures recommended will give good sections of exceptionally large areas (up to, and above 1 cm x 1 cm) of fully hardened blocks available at all points for electron microscopy. On such large blocks fully correlative, combined light and electron microscopy may be carried out easily. The process is termed 'hot knife microtomy'. In three different laboratories, primary aldehyde fixation by perfusion and hot knife microtomy have given uniformly excellent data from normal, diseased, and virus-infected brain tissues. These techniques permit full neuroanatomical control and orientation, make comprehensive correlative mapping throughout the CNS feasible, and allow study of the time course of infective processes.