Complex sentence: To check the status of salivary glands and the production of saliva, a salivary flow-rate test is performed, in which the person is asked to spit as much as they can into a cup, and the resulting saliva sample is collected and weighed.
Split into simpler sentences: To check the status of salivary glands and the production of saliva, a salivary flow rate test is performed. Here, the patient is asked to spit as much as he or she can into a cup, and the resulting saliva sample is collected and weighed.