The Pyloric Canal

THERE is now a considerable agreement in the general descriptions of the form, subdivisions, and functions of the stomach. It is a specialised organ of the post-cesophageal region of the fore-gut, limited distally by the pyloric sphincter; and it serves for the temporary storage of the swallowed food, which undergoes changes in its physical constitution during its storage. These changes are produced (1) by physical processes, such as the saturation of the food with fluids and its physical comminution and division, which have as their end the trituration and suspension of the food in fine granular form in the stomach fluids; and (2) by chemical processes, at least they are usually so named, which begin the gross molecular disintegration of the food, and are steps leading to its solution.l The fluids used in the physical processes are products of the gastric mucous membrane, while the physical division of the food is mainly effected by the pressure movements of the muscular wall of a part of the stomach, which is always recog-nisable and usually is a distinct region of it. This region is generally known as "the mill of the stomach"; the musculature of its walls is thicker, usually it is specialised in its arrangement and often it is distinctive in its structure; and its *A 'B Fig. 1 The primary parts of the stomach. mucous membrane is usually different from that of the receptive "non-milling" region, sometimes grossly so, sometimes only in the type of its glands. The "milling region" is always at the distal end of the stomach, immediately previWs 1. I am not now concerned with the discussion of which processes are phylogenetically the older or fundamentally the more important; or of the different forms of "the reciprocal balance" of the two processes in different animal groups, so that now the one process and now the other plays the larger part in the food changes; or of the relation of this balance to the nature of the food and the treatment to which it is subjected in the mouth.