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Show 174 MESSRS. SCHAFER AND WILLIAMS ON THE [Jan. 18, Two such clefts of considerable size are seen between the glands in fig. 5 ; other smaller clefts, also for the most part representing sections of lymphatics, are seen in the interglandular tissue in various parts of the mucous membrane. It will be observed, moreover, that the lymphoid tissue at the base of the glands is more abundant here than in the rest of the second region (fig. 2), with the exception of the lymphoid patches, and that the prolongations of the muscularis mucosae towards the surface between the glands are more numerous (mi .mi). The Mucous Membrane of the Third Region.-This is very thick both in Dorcopsis luctuosa and in Macropus giganteus, the thickness being as usual due to the length of the gland-tubes. These resemble in many respects the pyloric part of the second region just described; thus they are long straight tubes lined near the orifice with columnar epithelium, and in all the rest of their extent with small cubical or polyhedral cells, which in many parts nearly fill up the tubes. But there is this important difference, that superadded to these and situated outside of them (but still within the basement membrane, which they often cause to bulge outwards) there are, in the middle parts of the length of the gland (figs. 6 & 7), certain other cells of a spheroidal or ovoidal shape and granular appearance. These are what have long been known as peptic cells ; since it is believed, although it has not yet been conclusively proved, that they are the source of the pepsin of the gastric juice. They were termed by Rollett* the delomorphous cells of the gland, whilst the other, more centrally situated, and usually less obvious cells, which are continuous above with the columnar epithelium of the surface, he has termed adelomorphous. For the present it will be better to adhere to the old terminology (peptic cells) for the rounded cells, and to term the angular ones, which line the whole tube within them, central cells. The glands, moreover, in which the peptic cells occur we may continue to term the peptic glands, and the region of the stomach occupied by them the peptic region, without at the same committing ourselves so far as to maintain that the other portions of the stomach do not also, as some physiologists think, yield pepsin. To return to the structure of the glands. The spheroidal peptic cells vary in number in different glands, being fewest in the parts of the peptic region which are nearest the boundary between this and the second or general glandular region. It frequently happens that these peptic cells do not reach the fundus (b) of the gland, which is not larger in these glands than the rest of the tube, and is occupied exclusively by central cells which resemble the cubical cells of the other glands, but are smaller and more closely packed. The distribution of the peptic cells in the glands is well shown in fig. 6, which is a sketch of part of a vertical section from the middle of the peptic region as seen under a low power. The preparation was stained with aniline blue, according to Heidenhain's directions f; the peptic cells become much more deeply stained by this than the rest * TJntersuchungen, 1871. t Arch. f. mikr. Anat. vi. 1870. |
