The stomach has two muscular motions. The first is a turning movement, which takes place in the larger or cardiac portion, mixing the food with the gastric juice, thus bringing the whole to a semi-fluid consistency.
The second is a wave-like movement which takes place in the pyloric end, by means of which the food is allowed to pass by intervals into the duodenum, which is the entrance to the small intestine.
The juice poured out in the pyloric portion contains no hydrochloric acid, but is neutral or slightly alkaline; pepsin is present.
The quantity of gastric juice varies not only in different individuals, but in the same individual according to the diet. Extremes in temperature exert an influence on gastric digestion. Pawlow has made many very interesting experiments along this line, and has discovered that a diet composed chiefly of meat produces a large flow of gastric juice poor in ferments; bread produces a small flow of gastric juice rich in ferments; while milk produces a moderate flow of gastric juice and a moderate amount of ferments. To keep in good normal condition without gain or loss of body weight, a plain, wholesome, mixed diet is the most satisfactory.
There is great danger, especially in the young, of becoming addicted to digestive habits. Each food calls forth a special gastric juice, and if the diet is limited to a few foods the power to assimilate others becomes lessened; therefore if the diet is increased, gastric disturbances are apt to occur. When a patient has been kept for some time on a milk diet, other foods must be introduced gradually, and in small quantities, for the comfort of the individual.
The stomach being capable of great distension, often gives rise to the taking of too much food at a single time. Three meals daily meet the needs of the average person. Dinner should be the heartiest meal, and should be served after the work of the day is over, when sufficient time may be allowed for eating, which may be followed by rest.
