The wall of the intestine is composed of mucous membrane, submucous tissue, and muscle. The mucous membrane is everywhere pitted with tubular glands, termed in the stomach “gastric glands,” and in the intestines, both small and large, “crypts of Lieberkühn.” Their relation to the wall might be exemplified by taking a block of dough about 6 inches thick and pushing a pencil vertically into it almost down to the table on which it rests. The holes should be made as close together as possible, since, especially in the stomach, extremely little tissue intervenes between the tubes of gland-cells. If the piece of dough were placed upon a folded cloth, the cloth would represent the muscularis mucosæ, a layer properly regarded as a constituent of the mucous membrane. The fibres of this coat are disposed in two or three sheets, the fibres of one sheet crossing those of the next. By their contractions they squeeze the ends of the crypts, and probably wobble them about, expelling their secretion. Beneath the muscularis mucosæ is a layer of connective tissue, the submucosa, which contains abundant lymphatic channels, bloodvessels, and nerves. At the pyloric end of the stomach, the tubes of gland-cells tend to pierce the muscularis mucosæ. In the first part of the duodenum, certain tubes, having pierced this layer, branch in the submucosa. A layer of racemose glands is thus formed—the glands of Brunner. Outside the submucosa is the muscular coat proper, composed of plain muscle-fibres, except in the upper part of the œsophagus, where the fibres are striated. It consists of an inner and an outer sheet, the fibres being disposed circularly in the inner, longitudinally in the outer sheet, with a slight departure from this regular arrangement in the wall of the stomach. On its outside the canal is invested by peritoneum, a layer of flattened epithelial cells supported by connective tissue. The abdominal wall also is lined with peritoneum. The smooth moist surface of the peritoneum covering the intestines glides on the peritoneum lining the abdominal wall. Between the two is a “potential” space. In dropsy, fluid accumulates within this space. In a healthy condition the apposed surfaces are merely moist.