814 ME. G. S. WEST ON THE BUCCAL GLA-l^DS AITD [NoV. 19, 



to brown. The latter decreases in bulk anteriorly and opens 

 into the 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 

 (PL XLIV. 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 fi and an average internal diameter of 17 fj.. 

 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 salivai'y 

 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. XLIV. 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 

 veiy 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 had 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 stiU within the gland, has an epithelium 

 of narrow columnar cells with basal or central nuclei (PI. XLIV. 

 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 the cell being quite clear and I'esistant to the action of stains 

 (PI. XLIV. 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 



^ 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 descrijjed above. 



