By Harry Campbell, M.D., F.R.C.P. (Lond). Physician to the Northwest London Hospital. [London Lancet, July 11, 18, 25, and August 8, 1903]

The Effects of Mastication The primary object of mastication is to break up the food so as (1) to facilitate the swallowing of it, and (2), still more important, to insure its intimate admixture with the digestive juices, not only within the mouth, but throughout the entire digestive tract. Mastication has, however, other important and far-reaching effects. Thus it promotes the flow of saliva and, when properly performed, secures a due insalivation of the food; it increases the quantity of alkaline saliva passing into the stomach; it stimulates the heart and circulation; and it finally influences the nutrition of the jaws and their appendages by stimulating the local blood and lymph circulation. Now to consider these various objects and effects of mastication.

Mastication Acts Reflexly Upon The Stomach

It is now known that the act of mastication influences the stomach reflexly, promoting the flow of gastric juice and thus preparing the stomach for the entrance of food into it. If the oesophagus of a dog is cut so as to allow the swallowed food to escape instead of passing into the stomach, it is found that the mastication of food causes a considerable flow of gastric juice. Food introduced into the stomach unaccompanied by mastication is less effective in promoting the gastric flow. It is probable that the influence of mastication on the flow of gastric juice is largely produced through the medium of psychic influences, for the more efficient the mastication the more is the sense of taste affected.

Mastication Stimulates The Heart And So Promotes The General Circulation

This stimulating action may be partly due to its local action on the flow of blood and lymph in the jaws and accessory parts, and partly to a reflex influence, but whatever the explanation there can be no doubt of the fact. Hence the mere chewing of a non-nutritive substance, such as gum arabic, is stimulating, and, doubtless, the stimulating effects induced by the chewing of such articles as tobacco and betel are largely to be explained in this way.

The Influence Of Mastication On The Jaws And Adjacent Structures

This subject is of such importance that it needs to be dealt with in some detail. By "adjacent structures" I mean the masticatory muscles, tongue, teeth, salivary glands, the nasal passages and sinuses pertaining thereto, the naso-pharynx, soft palate, and tonsils.