  After recalling some connections between the Spontaneous Breakdown of Chiral
Symmetry (SBChS) and the spectrum of the Dirac operator for Euclidean QCD on a
torus, we use this tool to reconsider two related issues : the Zweig rule
violation in the scalar channel and the dependence of SBChS order parameters on
the number N_f of massless flavours. The latter would result into a great
variety of SBChS patterns in the (N_f,N_c) plane, which could be studied
through so-called Leutwyler-Smilga sum rules in association with lattice
computations of the Dirac spectrum.
