A

51-year-old man with six children comes in for a vasectomy. In this outpatient

procedure, the lateral wall of the scrotum is opened under local anaesthesia and

a portion of the ductus deferens is excised. The free ends are clipped or

sutured and the scrotum is closed. As part of a normal histological description

of the removed portion, the report would certainly describe the presence of

what structure?