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Show 1876.j MUCOUS MEMBRANE IN KANGAROOS. 169 orifice are only slightly marked in the stomach of Macropus. Tbe second region (B) has a greater extent in Macropus giganteus than in Dorcopsis. It occupies all the rest of the inner surface of the stomach except (as in Dorcopsis) a circular patch (C) about 3 inches in diameter, situate at the pyloric fundus, and not marked off from the rest by any well-defined naked-eye appearances except the great thickness of the mucous membrane. But microscopical examination shows that the glands of this patch present material differences from those of the rest of the stomach, whilst resembling those of the corresponding part of the Dorcopsis stomach ; so that this patch is to be taken as representing the third region in Macropus also. The tract n, moreover, which passes in Dorcopsis over the upper part of the stomach in this place, is also represented in Macropus. The second region m a y be said to commence at the extreme end of the cardiac fundus, where its mucous membrane lines the pouch (p) above referred to as not being covered by the hard gullet-epithelium ; from here it passes to the right, along the greater curvature of the stomach, gradually narrowing at first, so that opposite the oesophagus it forms a strip only about | of an inch wide, bounded on either side by the epithelium of the first region, but subsequently becoming gradually wider until it extends continuously round the organ. In both animals the mucous membrane of the second region has here and there insular elevations flattened on the surface and beset all over with small rounded eminences, each with a little pit at its summit as if made with the point of a pin. These elevated patches vary in size, but seem to have a fairly regular distribution (Diagrams 1 and 2, /, I). Thus in both animals there is a large triangular patch on each wall of the stomach, the base of which is close to the third region of the mucous membrane, while the apex of the triangle extends upwards and to the left towards the lesser curvature. From near the apex a chain of smaller and more circular patches is continued for some distance parallel to the line of demarcation between the first and second regions-in Dorcopsis, in fact, as far as the second region extends. As the result of microscopical examination clearly shows, these elevations are owing to accumulations of lymphoid tissue in and beneath the mucous membrane; and they may therefore be termed "lymphoid patches." They are in many respects analogous to Peyer's patches of the small intestine. Microscopical Characters of the Mucous Membrane. The results of the microscopical examination of the several regions correspond for the most part in both animals (as might indeed have been expected in genera so closely allied); so that the same description will apply to both. W e shall afterwards take the opportunity of pointing out any special peculiarity which may obtain in either. The figures, which have been taken indiscriminately, some from the one animal and some from the other, will, for the most part, serve to illustrate the structure of the corresponding parts in both. The Mucous Membrane of the First Region.-This is covered with a coating of dense stratified epithelium (Plate VIII. fig. 1, S) con- |
