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Show 272 P B O V E N T E I C U L A B O E Y P T S O F P S E U D O T A N T A L U S IBIS. [Mar. 19, and conspicuous apertures of the glands, and the two circular areas form thick pads that may be seen and felt from the outside before the stomach is opened. The figure in the text (p. 271) represents the proventriculus laid open, with the two circular areas conspicuous opposite the reference letter b. Above these, in the African Tantalus, is a single irregular row of pits, of different sizes and about twenty in number. In the figure the row is shown opposite the reference letter a, and at d an enlarged view of one of them is given. There is no trace of these pits or crypts in the other birds with similar proventriculus that I have examined. Each crypt is a shallow circular or oval pit, the margin of which is slightly elevated. From the floor of the crypt rise a system of crescentic folds of different sizes. As the bird was tolerably fresh when I examined its intestine, I prepared microscopic sections through one of the crypts. The drawing (Plate XVII. fig. 1) represents one of these seen under a low power, e, f, and g are placed opposite the ends of the crescentic folds, the letter </ being placed within the cavity of the crypt. The surface of these folds is set thickly with a number of small villi, and these are continued over the raised margin of the wall of the crypt. Fig. 2 represents some of these villi seen under higher magnification. The whole of the pit is lined by an epithelium continuous with that lining the general surface of the proventriculus (fig. 1, ep, fig. 2, ep, Jc & m). Over the general surface this is an ordinary columnar epithelium, but here and there between the villi, as at m, it becomes glandular. At fig. 2, 1c, two of these glandular infoldings are seen in cross-section. Immediately under the epithelium seen at a, in fig. 1, and forming the solid mass in fig. 2, is a dense connective-tissue layer. This contains fibres and cells, and here and there capillaries and absorbents. This layer forms the greater part of the villi and lies next to the epithelium on the summits of the crescentic folds. But further down, in the cavity of the crypt, masses of lymphatic tissue (fig. 1, c) lie between the connective tissue and the epithelium. Here and there bands of connective tissue invade the masses of lymphatic cells and separate islands of them from the main mass. This layer of lymphatic tissue was the most conspicuous part of the sections, and as in some of them the epithelium had been destroyed it closely resembled a granular cuticular layer. Under the connective-tissue layer was a thicker layer consisting of a loose stroma containing fibres, connective-tissue cells, and blood-vessels. The deeper part of the section (fig. 1) passed through some of tbe follicles of the proventricular glands. Each of these was surrounded in the ordinary way by a capsule of connective tissue. I confess that I a m unable to form any clear conception as to the function of these crypts. It is possible that they m a y serve for the absorption of water or of fluids. From the position of the stomach in the body, these crypts must lie very little above the level of the |
