  Jean-Marie Souriau's book ''Structure des syst\`emes dynamiques'', published
in 1970, republished recently by Gabay, translated in English and published
under the title ''Structure of Dynamical Systems, a Symplectic View of
Physic'', is a work with an exceptional wealth which, fifty years after its
publication, is still topical. In this paper, we give a rather detailled
description of its content and we intend to highlight the ideas that to us, are
the most creative and promising.
