I argued that if Nature had given us personal responsibility it was not hidden away in the dark folds and coils of the alimentary canal where we could not control it. The fault or faults must be committed before the food was swallowed. I felt instinctively that here was the key to the whole situation. The point, then, was to study the cavity of the mouth; and the first thought was: "What happens there?" and "What is present there?" The answer was: Taste, Smell (closely akin to taste and hardly to be distinguished from it), Feeling, Saliva, Mastication, Appetite, Tongue, Teeth, etc. I first took up the careful study of Taste, necessitating keeping food in the mouth as long as possible, to learn its course and development; and, as I tried it myself, wonders of new and pleasant sensations were revealed. New delights of taste were discovered. Appetite assumed new leanings. Then came the vital discovery, which is this: I found that each of us has what I call a food-filter: a discriminating muscular gate located at the back of the mouth where the throat is shut off from the mouth during the process of mastication. Just where the tongue drops over backward toward its so-called roots there are usually five (sometimes seven, we are told) little teat-like projections placed in the shape of a horseshoe, each of them having a trough around it, and in these troughs, or depressions, terminate a great number of taste-buds, or ends of gustatory nerves. Just at this point the roof of the mouth, or the "hard palate," ends; and the "soft palate," with the uvula at the end of it, drops down behind the heavy part of the tongue. During the natural act of chewing the lips are closed, and there is also a complete closure at the back part of the mouth by the pressing of the tongue against the roof of the mouth. During mastication, then, the mouth is an airtight pouch. After which brief description, please note, the next time you take food, WHAT HAPPENS DURING MASTICATION Hold the face down, so that the tongue hangs perpendicularly in the mouth. This is for two reasons: one, because it will show how food, when properly mixed with saliva, will be lifted up in the hollow part in the middle of the tongue, against the direct force of gravity, and will collect at the place where the mouth is shut off at the back, the food-gate. It is a real gate; and while the food is being masticated, so that it may be mixed with saliva and chemically transformed from its crude condition into the chemical form that makes it possible of digestion and absorption, this gate will remain tightly shut, and the throat will be entirely cut off from the mouth. But as the food becomes creamy, so to speak, through being mixed with saliva, or emulsified, or alkalised, or neutralised, or dextrinised, or modified in whatever form Nature requires, the creamy substance will be drawn up the central conduit of the tongue until it reaches the food-gate.