18/6.] MUCOUS MEMBRANE IN KANGAROOS. 173 



of the one blends with that of the other. In this particular, as in 

 most others, the lymphoid patches of the Marsupial stomach exactly 

 resemble the patches of Peyer of the human ileum, only that in the 

 latter the lymphoid follicles occupy more of the mucous membrane 

 and come entirely to the surface, whereas, in the gastric patches in 

 question, the follicles, as well as the remainder of the lymphoid 

 tissue, are surmounted by tubular glands, except at the centre of 

 each, where the surface is pitted in as far as the summit or cupola 

 of the follicle. The glands over these lymphoid patches are some- 

 what shorter than those which are found in the rest of the mucous 

 membrane of the second region, but entirely agree with them in 

 structure (figs. 3 & 4). 



Transition of the Stratified Epithelium of the First Region into the 

 simple Columnar Epithelium of the Second Region. — The manner in 

 which this occurs will be readily understood by again referring to 

 fig. 1. Close to the hmit between these two regions the stratified 

 epithelium {S) of the first is of considerable thickness, nearly as thick, 

 indeed, as the whole mucous membrane of the second. If the lower 

 line of the epithelium be followed, it will be seen that just as it ap- 

 proaches the junction it rises rather abruptly towards the surface, the 

 layers of cells above it being continually less and less numerous until 

 they are reduced to six or eight only. The lowermost columnar cells 

 (c) of the stratified epithelium then become directly continued into 

 the simple columnar epithelium (c) of the glandular region, whilst 

 the layers above it cease abruptly, one or two cells often projecting 

 at the edge like bricks from the end of a wall. The tubular glands 

 begin immediately beyond this, the first ones passing down parallel 

 with the ascending line of the stratified epithelium ; but they are 

 separated from it by somewhat more of the tissue of the mucosa 

 than they are from one another. This tissue (?, i) contains very 

 numerous lymphoid cells, and many are seen also in between the 

 lower cells of the stratified epithelium of the immediate neighbour- 

 hood (at ly). Transitional forms of epithelium between the scaly 

 stratified and the columnar (as described by Henle at the line of 

 transition of gullet into stomach-epithelium in man) do not occur, 

 but the passage of the one into the other is quite abrupt and effected 

 by the cessation of all the layers of the stratified epitheUura except 

 the lowermost. 



Structure of the Second Region, in the neighbourhood of the 

 Pylorus. — The lining membrane as well as the muscular coat is here 

 very thick, especially in Macropus giganteus ; and the gland-tubes 

 are correspondingly long (fig. 5). They are not enlarged at the 

 fundus ; and the cells of this are similar in appearance to those of the 

 rest of the tube. Numerous bundles of muscular tissue {m' . m!) pass 

 from the muscularis mucosae upwards towards the glands. But the 

 most striking feature of the part is the number and size of the 

 lymphatics {I, I). These appear in sections as large well-defined 

 clefts in the connective tissue between the glands. The clefts are 

 not merely accidental ; for they have a definite wall of flattened 

 nucleated cells, like the commencing lymphatics elsewhere. 



