1. The laws of intestinal peristalsis are explained by the structure of the intestinal wall. The intestine can be represented schematically as two tubes, one inserted into the other, as a gun lube constructed with due consi­deration for the strongest pressure produced in it. One tube (outer) consists of the serous and muscle coats, whereas the other (inner) is formed of the mucous coat and its lamina muscularis. Both tubes can slide one in relation culature in the form of three mus­to the other due to the presence of the submucous layer of connective tissue containing the main mass of the vessels and making movement easier. The connective-tissue fibres of the submucosa and of all the other coats pass spirally in the oral-caudal direction with which coincide the course of the muscle fibres of lamina muscularis and the direction of the spiral layer of the muscle coat. The tube experiences pressure from inside under the effect of the intestinal contents; the inner tube in such instances dilates uniformly because the bundles of connective and muscular tissues have the same direc­tion; the outer tube dilates irregularly because the direction of its muscle layers (longitudinal and circular) differs from that of the connective-tissue fibres penetrating the muscles. Bearing in mind the spiral course of all the connective-tissue and some of the muscular fibres (the spiral layer of the muscular coat and the muscularis mucosae), the predominance of the spiral construction of the wall of the small intestine must be recognized. The spiral construction determines the polarity of the peristalsis of the small intestine from the oral to the anal pole and under normal conditions prevents antiperistalsis. The large intestine has circular musculature as the result of the marked predominance of the circular musculature. Besides peristaltic movements, antiperistaltic movements occur, therefore, in the large intestine, which promote mixing and formation of the contents. 2. Both anatomical layers of the intestinal wall differ in function: the mucous coat is concerned with absorption and secretion, the muscular coat accomplishes the motor function. The correlation between these two functions change along the length of the intestinal tube and there are consequently areas with the predominance now of motor, now of other functions. In accor­dance with this, as it is claimed by some authors, there is the alternation of segments differing in the structure of the intestinal wall (its mucous and muscle coats, as well as nerves and vessels). The principal evidence of the alternation are changes of the intramural blood vessels, because these are associated with metabolism.