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Show 814 MR. G. S. WEST ON THE BUCCAL GLANDS AND [Nov. 19, to brown. The latter decreases in bulk anteriorly and opens into tbe mouth by a series of about twenty ducts, which are arranged along the entire length of the gland, the orifices lying just within the inturned edge of the lowest lateral series of scales (PI. X L I V . fig. 15, d.s.l.), and consequently only just within the mouth. It really consists of a series of small closely adpressed racemose glands, the ducts near their orifices having an average external diameter of 65 p and an average internal diameter of 17 y.. The inferior labial gland extends along the outer face of the mandible, and is very similar in form to the superior labial gland, though as a rule it is not so elongated; it possesses the same arrangement of its ducts, though the number is more variable. Both these glands are disposed in such a manner as to hide to a great extent the maxillary and mandibular teeth. The structure of the labial glands is similar to that of a salivary gland with rather large alveoli. The gland-cells are shortly columnar (polygonal when seen from above) and the nuclei are basal in position ; the lining epithelium of the ducts, even up to their very orifices, consists of precisely similar cells. The cell-contours, nuclei, and that portion of the cell-contents immediately surrounding the nucleus stain very clearly. The alveoli of the poison-gland are smaller than those of the labial glands (PI. X L I V . fig. 17), though their size, as also the comparative size of their constituent cells, varies considerably in the different genera of this group. The nuclei stain clearly, but the cell-contours and the finely granular cell-contents often stain very indistinctly; this will depend on the condition of activity of the gland. The Ehrlich-Biondi mixture was much used for staining sections of this gland and answered very well, if, after the sections had remained some time in that mixture, they were placed for a brief period in a very weak solution of picric acid; this bad the effect of fixing the methyl green in the nuclei. The duct of the poison-gland is very much larger than any of the ducts of the labial glands ; it passes inwardly and downwardly and takes a slightly forward (or rarely a backward) direction from the gland. The duct, whilst still within the gland, has an epithelium of narrow columnar cells with basal or central nuclei (PL X L I V. fig. 18), but when nearing its point of exit the epithelial cells become larger and of different lengths with their bases somewhat pointed. Other polygonal cells are also present outside them, fitting into the interstices resulting from the different lengths of these cells. The nuclei are here situated at the extreme bases of the cells and are embedded in a denser cup-shaped mass of protoplasm, the rest of tbe cell being quite clear and resistant to the action of stains (PI. X L I V . fig. 19). These cells are typical mucus-secreting cells, precisely similar to those of the mucous membrane of the mouth \ The duct either opens into the cavity formed by the muscular folds 1 The mucous membrane of the mouth of this group of Snakes is thrown into a series of longitudinal folds and the epithelium consists entirely of similar secretory cells to those described above. |