26. MOVEMENTS OF THE STOMACH.--The inner coating of the stomach is the mucous membrane, which, as we have seen, furnishes the gastric juice. Next to this coating lies another, called the muscular coat, composed of involuntary muscular fibres, some of which run circularly, and others in a longitudinal direction. These expand to accommodate the food as it is introduced, and contract as it passes out. In addition, these fibres are in continual motion while food remains in the stomach, and they act in such manner that the contents are gently turned round from side to side, or from one end of it to the other. [Sidenote: 27. Peristaltic movements? What is said of our consciousness of and power over these movements? Describe the movements of the pylorus.] 27. By these incessant movements of the stomach, called the _peristaltic_ movements, the gastric juice comes in contact with all parts of the food. We are, however, not conscious that these movements take place, nor have we the power to control them. When such portions of the food as are sufficiently digested approach the pylorus, it {93} expands to allow them to pass out, and it closes again to confine the residue for further preparation. [Sidenote: 28. How has the knowledge and the workings of the stomach been ascertained? St. Martin? How else?] 28. The knowledge of these and other interesting and instructive facts has been obtained by actual observation; the workings of the stomach of a living human being have been laid open to view and examined--the result of a remarkable accident. Alexis St. Martin, a Canadian _voyageur_, received a gun-shot wound which laid open his stomach, and which, in healing, left a permanent orifice nearly an inch in diameter. Through this opening the observer could watch the progress of digestion, and experiment with different articles of food. Since that occurrence, artificial openings into the stomach of the inferior animals have been repeatedly made, so that the facts of stomach-digestion are very well ascertained and verified. [Sidenote: 29. What was formerly thought? What do we now know? What else do we now know? Water, salt, and sugar? Absorption?]