The stable and unstable manifolds of a saddle fixed point (SFP) of the
Bonhoeffer-van der Pol oscillator are numerically studied. A correspondence
between the existence of homoclinic tangencies (whic are related to the
creation or destruction of Smale horseshoes) and the chaos observed in the
bifurcation diagram is described. It is observed that in the non-chaotic zones
of the bifurcation diagram, there may or may not be Smale horseshoes, but there
are no homoclinic tangencies.Comment: 14 pages, 15 figure