2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/55288I describe some recent work in which classical solutions of Dirac-Born-Infeld theory may be used to throw light on some properties of M-theory. The sources of Born-Infeld theory are the ends of strings ending on the world volume. Equivalently the fundamental string may be regarded as merely a thin and extended piece of the world volume.11 pages Latex, no figures. This is the written version of a lecture given at "Quantum Mechanics of Fundamental Systems VI ", Santiago, Chile, August 1997 to appear in the Proceedings edited by C. Teitelboim and J. ZanelliHigh Energy Physics - Theorytext