This section is from the book "Practical Dietetics With Special Reference To Diet In Disease", by William Gilman Thompson. Also available from Amazon: Practical Dietetics with Special Reference to Diet in Disease.
In addition to exciting secretion upon entering the stomach, the food, at first by mechanical action and subsequently possibly through chemical stimulation, excites more or less rhythmical peristaltic movement in the muscular coat of the stomach. The object of this movement is fourfold: 1. To mingle the contents of the food thoroughly with the gastric juice. 2. To cause moderate trituration of the particles of food which are made to move in currents that proceed along the greater curvature and pass back to the cardiac end along the lesser curvature. 3. To bring the food in contact successively with different portions of the mucous membrane, and to thus stimulate it and favour the absorption of such ingredients as this division of the alimentary canal is capable of taking up. 4. To favour the occasional emptying of a portion of the contents of the stomach into the duodenum, the movement at this time being accompanied by a relaxation of the pyloric orifice.
Peristaltic action is influenced by the nature and composition of the food ingested, and it may be also stimulated in other ways, which will be more fully described in connection with intestinal peristalsis (see Diarrhoea and Constipation), for it may be said in general that those stimuli which effect intestinal peristalsis also influence this peculiar movement in the stomach.