Of the numerous theories of the pathogenesis of tabes dorsalis, only two deserve consideration. According to one theory, advocated by Strümpell,1 Spielmeyer,2 Hauptmann3 and others, tabes is an endogenous disease process. It is supposed to be caused by a syphilitic toxin which "selectively" affects certain parts of the posterior columns and causes their degeneration. The other, equally popular, theory is that tabes is an exogenous disease, which originates outside the spinal cord, either at the so-called area of Obersteiner-Redlich or in the "radicular nerve" of Nageotte.
Obersteiner and Redlich4 called attention to the fact that at the place of their passage through the pia, the posterior roots "seem to be deprived" of some of their myelin, and, as a result of this, exhibit there a visible constriction; as the axons in this area lie unprotected and naked, they become the "locus minoris resistentiae," that is, particularly