Golgi and Ranvier: from the black reaction to a theory of referred pain.

In his brief report on the structure of the gray matter of the central nervous system (1873), in which he described the "black reaction", Golgi noted the ramifications of the axon. This discovery prompted the French histologist Louis Antoine Ranvier, one of the first to try the black reaction outside Italy, to propose an ingenious theory of referred pain in his Traité technique d'histologie. Ranvier suggested that the nerve fibers originating from the irritated area and those coming from the region to which the sensation is referred converge on the same axon and thus the same cell body, causing the spatial dislocation of sensation. This theory of referred pain is a powerful example of the extraordinary clinical-physiological impact of the first of Golgi's neurocytological discoveries.