Srimad-Bhagavatam: Canto 3 - Chapter 1 - Verse 20
Sanskrit:
गुदं पुंसो विनिर्भिन्नं मित्रो लोकेश आविशत् ।पायुनांशेन येनासौ विसर्गं प्रतिपद्यते ॥ २० ॥
ITRANS:
gudaṁ puṁso vinirbhinnaṁmitro lokeśa āviśatpāyunāṁśena yenāsauvisargaṁ pratipadyate
Translation:
The evacuating channel separately became manifest, and the director named Mitra entered into it with partial organs of evacuation. Thus the living entities are able to pass stool and urine.