1. A description is given of the value of ‘spreading factor’ (hyaluronidase) used in conjunction with various neurohistological methods for the display of tissue neural elements.
2. It has been shown that after its use nerve fibres and their terminals in a variety of tissues, including the cornea, closely resemble those seen in fresh specimens of cornea under phase-contrast conditions.
3. The specimens prepared after treatment with hyaluronidase are almost free from artifacts. The staining or impregnation process can be controlled with certainty and precision to produce evenly stained specimens in the tissues we have used.
4. It is suggested that some tissues may need special treatment to obtain optimal results.
5. The use of ‘spreading factor’ makes it possible to determine the cause of the artifacts commonly observed after employing standard neurohistological techniques.
6. The rationale of using ‘spreading factor’ in conjunction with neurohistological techniques is discussed.