The rapid rhythm of material and psychic evolution that the non-industrialized (or insufficiently industrialized) societies of the African continent follow in this day and age inevitably outdates the writings of ethnologists at a similar tempo.

Nevertheless, the correctives that can be brought to bear on a vertical section often appear less considerable than the spectacular surface changes would have us presume. This is due, quite simply, to the remarkable resistance of the deep layers of the soul which conceal the obscure dynamic forces that model mentality or, if one prefers the expression, the ethnic personality.