The Marchi method was originally devised for and has been extensively used as a means for working out the finer details of neuroanatomy. Its value for this purpose lies in the fact that it is the most convenient and on the whole the best method for following myelinated nerve fibers which are undergoing active degeneration as a result of accidental or experimental lesions. Although it is generally conceded that the use of the method requires considerable experience, it is the accepted technic on which much of present knowledge of fiber tracts is based. The method has also been used extensively in studying the histopathology of the nervous system, particularly that of the peripheral nerves. A review of the literature and some original work on this use of the Marchi technic have convinced me that its value for such purposes is limited, and that much confusion has arisen as a result