[Old theories and present-day hypotheses for the mechanisms of erection]

On the basis of old theories and recent observations, the authors discuss the real nature of the activity of the erectile tissue of the corpora cavernosa and spongiosa. Is erection simply produced by passive injection of spongy tissue? Or is erectile tissue like a real live "sponge" which is capable, on its own, of producing and eliminating erection? If this is the case, where is the intra-tissue motor apparatus located? A new hypothesis is proposed.