In the investigations that form the basis for a series of papers on nerve degeneration in experimental poliomyelitis, of which this is the first, a search was made for a vital dye that would reveal simultaneously changes in the nerve cells of the spinal cord and in the root fibers. Neutral red was found to fulfil this requirement, and the present communication is concerned with a presentation of the methods whereby intravital staining of degenerating nerve fibers may be obtained. Since the course of wallerian degeneration is best known in peripheral nerves severed from their cells of origin, we decided to standardize the methods presented on this basis. It is recognized that modifications may be necessary as needs other than ours become apparent. A review of the literature shows that since Ehrlich's1discovery, in 1886, that methylene blue colors the neuraxon but few additional methods have been forthcoming for