This method consists of: (1) cutting formalin-fixed frozen sections 160μ thick of the brain of experimental animals, (2) mounting the unstained sections in glycerol under a cover slip, and (3) photographing their enlarged images on Kodak Direct Positive paper. The results resemble photographs of myelin sheath preparations. Direct positive photography eliminates the time needed for tediously tracing projected images, usually done on stained sections. With this method it is possible to obtain a histological analysis of a neurophysiological experiment on the following day.