The idea that the nerve-cell protoplasm has a fibrillary content dates back to the time of Max Schultze. Histologists were, however, in doubt about the matter until Apáthy, a Hungarian scientist, with the use of a difficult and complicated method, devised by himself, demonstrated the fibrils convincingly. The method of Apáthy, however, yielded very inconstant results, and, moreover, often failed entirely in the hands of other investigators. Beside, the method was applicable only to the tissues of invertebrates, mammalian and other vertebrate tissues failing to respond to the stain. Apáthy, by his demonstrations before various anatomic societies, was nevertheless able to convince research workers in his field that the fibrils actually exist.
A search for a method which would stain the neurofibrils in human tissues was rewarded by the discovery by Bethe of a procedure which stains tolerably satisfactorily the fibrils in normal adult nerve cells. Bethe's method is also