The Distribution of Mast-Cells in the Digestive Tract of Laboratory Animals: Its Bearings on the Problem of the Location of Histamine in Tissues

The mast-cell distribution in the digestive tract of the rat, dog, cat, and guinea-pig was studied. In the rat mast-cells were present in the tongue, oesophagus, and forestomach, but practically absent from the glandular stomach, duodenum, ileum, and rectum. In the other species, mast-cells were numerous throughout the whole of the digestive tract, presenting a large individual variation. In the tongue and oesophagus mast-cells were found mainly in the submucosa and lamina propria, where they were located near the epithelium. In the stomach, mast-cells were more numerous in the mucosa and concentrated in the muscularis mucosae and between the necks of the glands. In the duodenum, mast-cells were also more numerous in the mucosa, being concentrated in the muscularis mucosae and frequently also in the summit of the villi. In the ileum and rectum mast-cells were less numerous than in the stomach and duodenum, keeping the same disposition as in these. The contribution of the mastcells to the histamine content of the digestive tract is discussed.