FIGURE 3. Actual time–activity curves of parotid glands (curves A and B), submandibular glands (curves C and D), and oral cavity (curve E) in 60-y-old healthy man. Parotid gland curves show monotonic uptake until stimulation; submandibular curves show spontaneous secretion, and oral cavity curve reflects resultant activity in mouth. Arrow marks lemon juice stimulation point.