2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/54798In the lectures given at '96 Kashikojima Summer Institute, Amagi-Highland Seminars, and Yukawa Institute Workshop, the old-fashioned dualities and the theory of extended objects are reviewed, starting from 't Hooft-Mandelstam duality and following the author's old works. Application of the old-fashioned dualities to new issues are also given on the D-branes, on the phase transition of B-F theory to Einstein gravity and on the swimming of microorganisms.Latex file, 21 pagesHigh Energy Physics - Theorytext