Q. A 78 year-old man presents with episodic bouts of hearing loss, ear ringing, and a "spinning sensation" to the right. This has been going on and off intermittently for years. It can be quite debilitating when it occurs. You decide to prescribe him furosemide (a diuretic) to see if it will reduce the severity of his symptoms and decrease the occurrences. Which of the following ducts in the inner ear is low in sodium and high and potassium?