522 MR. a. s. WEST on the histology of 



glands, I can fully confirm for those genera that I have ex- 

 amined. These lobules are difficult to stain, and the alveoli and 

 cells have a different structure to the rest of the gland. 



Certain peculiarities are to be found in the poison-glands of 

 the Marine Snakes (Hydrophiinse), some of which I have already 

 described *. The inter-alveolar connective tissue is extensively 

 developed, this being very noticeable in 'Enliydris HardwicTcii ; 

 and Platurus fasciatus is conspicuous for the small size of the 

 external alveoli, especially at the posterior end of the gland. 

 Fig. 7 represents a portion of four alveoli from the gland of 

 Distira cyanocincta, after secretion. The duct, in this group of 

 snakes, is also remarkable for the convoluted course taken by 

 its terminal portion. Small lobules are found arranged round 

 its course as in the other Proteroglyphous Colubridse ; and in 

 I*lafurus fasciatns these glands are reduced almost to single 

 alveoli with a lining epithelium like that of the poison-gland 

 itself; but in Distira cyanocincta and Hydrus platurus they are 

 more conspicuously developed, a few of them in the latter half 

 of the course of the duct ultimately becoming mucus-secreting. 

 Towards the termination of the duct, the cells of its own lining 

 epithelium also become mucus-secreting in the above two species 

 and possibly in others ; this has been shown to be normal in the 

 ducts of the parotid and labial glands of the Opisthoglyphous 

 Colubridse, but in the Crotalidse the lining epithelium is a 

 pavement one f. Moreover, as the epithelium of the duct of the 

 submandibular poison-gland of the Saurian reptile Eeloderma 

 suspectum has been shown by Holm % to have no secretory 

 function, it would appear that this function is confined to the 

 salivary (and poison) ducts of some of the Ophidia. Thus in the 

 Ophidia are to he found the only animals in which a considerable 

 admixiure of mucus is present in the parotid saliva, this mucus 

 being derived in all cases from some of the epithelial cells of the 

 duct and sometimes from special accessory mucous alveoli also. 



The presence of mucous alveoli in the parotid gland and the 

 conspicuous admixture of mucus in the parotid secretion, more 

 especially of Elapine Colubrine Snakes, may perhaps present an 

 analogy to the condition in the submaxillary gland of many 



* P. Z. S. 1895, p. 821. 



t S. Weir Mitchell, in Smithson. Contrib. Knowl. vol. xii. I860, p. 13. 

 \ Dr. J. F. Holm, " Some Notes on the Histology of the Poison-glands of 

 Helodeiina susjiectum^' Anatomischer Anzeiger, Baud xiii. Nr. 3, 1897, p. 84. 



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