The alimentary canal has an abundant supply of nerves from the vagus and the sympathetic systems. It contains also within its own wall an enormous quantity of nerve-fibres and nerve-cells. They are disposed as two plexuses, one in the submucosa, the other between the circular and longitudinal muscular coats. In a specimen successfully stained with methylene-blue, they are so abundant as to give the impression that every plain muscle-cell may have its own separate nerve-twig. Nevertheless, the contraction of the muscle-cells may take place independently of all nerve-influence—independently, even, of the local mechanism, the plexus referred to above. Nicotin applied to the wall of the intestine paralyses the local nerves; yet rhythmic contractions still occur. They are, however, no longer progressive. They do not drive the contents of the intestine forwards. Co-ordinated contraction is observed so long as the local mechanism is intact, even though all external nerves have been cut. The intestines have their own nerve cells and fibres, which, acting as a linked system of reflex centres, provide for the harmonious contraction of their walls. External nerves, sympathetic and splanchnic, convey impulses which either intensify the movements or inhibit them, as need may be. In the matter of its nerve-supply, the alimentary canal stands apart from the other organs of the body. It may be supposed that it presents a more primitive condition. Its muscular fibres have the power of contracting spontaneously. The pressure of the contents of the tube acts as a stimulus. When the fibres are stretched, they contract. When the tube is dilated, its muscles endeavour to restore it to its normal calibre. Such direct action would not, however, provide for the forward passage of its contents. To bring about peristalsis, a nervous mechanism is needed, as abundant and complicated as that which ensures the progress of a slug or a worm. To deal satisfactorily with the various contents of the tube—liquid, solid, gaseous—the mechanism must be capable of complicated adjustments. The dilated portions of the tube—stomach, cæcum coli, rectum—require special arrangements of muscle and nerve. Nor is the canal altogether independent of the rest of the body. To a large extent its work is carried on without regard to the activities of other organs, yet it is not wholly free from the control of the central nervous system. It is regulated by means of both afferent and efferent nerves of the vagus and sympathetic. Even the brain has something to say with regard to the way in which it shall contract. It is a matter of common experience that emotional influences may affect the movements of the stomach and intestines—“His bowels yearned.”