Scanning electron microscopic studies on lymphatic casts of the rat stomach and the rabbit small intestine

Under a scanning electron microscope, the lymphatic vessels of the rat stomach and the rabbit small intestine were observed by a corrosion casting technique. The structures thus revealed were compared with those embedded in Epon by a light microscope. On the mucosal layer of the rat stomach, the lymphatic casts showed various structures, i.e., fusiform casts from the subepithelial lymphatics, a basket-shaped structure from the interglandular lymphatics and a horizontal network of leaf-like structures from the subglandular lymphatics. These casts also showed several nuclear depressions about 10 μ in diameter, a number of constrictions, and numerous small holes representing reticular or collagen fibers interrupting the Mercox filling. The submucosal lymphatic casts of the rat stomach showed irregular tubular or flat shapes about 20-40 μ in diameter, nuclear depressions about 15 μ in their long diameter with sawtoothed figures around them, bead-like swellings, and occasional V-shaped incisura on parts of the columns. Similar findings were also observed in the submucosal layer of the rabbit small intestine. On the mucosal layer of the rabbit small intestine, the central lacteal casts showed peculiar figures, i.e., a dome-shaped structure about 70-80 μ in diameter at the topmost portion, swelling to about 100-200 μ in diameter in the middle, and an evident constriction to 30-60 μ in diameter at the bottom. Some of the morphological characteristics of the central lacteal at any site of the small intestine were clarified by this study: a) in the duodenum, three or four central lacteals within one villus formed pedunclar anastomoses branching from about half way up the lamina propria, b) in the jejunum, one or two lacteals within a villus had swellings just above the bottom constriction, and c) in the ileum, each villus contained only one lacteal with a swelling in a higher position