The anus and the membrum virile are two organs which exist for evacuation. The first is for evacuation of stools, the second for that of urine as also of the semen when one feels the influence of desire.
पायूपस्थं विसर्गार्थमिन्द्रिये तुल्यकर्मणी। विसर्गे च पुरीषस्य विसर्गे चापि कामिके॥