One problem you'll face as you age is that your mouth will produce less saliva, leading to dry mouth.
Xerostomia is a condition in which the mouth is dry because it does not produce enough saliva.
Snacking produces less saliva than a meal, leaving food bits in your teeth for hours longer.
Salivary glands are the parts of the mouth and throat that produce saliva.
A horse which does not produce saliva also does not mouth the bit.
Both of these conditions cause you to be unable to produce enough saliva.
When you become dehydrated, you do not produce as much saliva.
When we don't produce enough saliva, our mouth gets dry and uncomfortable.
Both of these test had some validity since a guilty person would produce less saliva and thus have a drier mouth.
Even before it was given the food, the dog began to produce saliva in response to the appetizing smell.