New theory on the mechanism of erection involving hitherto undescribed vessels.

47 cadaver penises were investigated by means of plastic, corrosion casts, direct dissection under a stereomicroscope, tissue clearing, and light microscopy. "Shunt" arteries connecting the deep arteries in the corpora cavernosa with vessels in the corpus spongiosum were found. When the penis is flaccid these arteries probably allow blood to pass through the corpora cavernosa directly into the veins of the corpus spongiosum. Constriction of the shunt arteries may divert blood through the helicine arteries into the spaces of the corpora cavernosa, thus producing tumescence and erection. 20 of the cadaver penises had no direct vascular connection between the corpora cavernosa and the corpus spongiosum or glans. This supports the hypothesis that such fistulae, which have been reported in impotent patients are pathological structures.