520 MK. G. S. WEST OK THE HISTOLOGY OP 



that Heidenhain's views on this point * are partially f correct so 

 far as the mucous glands of the Ophidia are concerned, otherwise 

 it would be impossible for a gland reduced to the condition of that 

 of fig. 10 to regain with requisite expediency its normal structure. 

 Another figure (fig. 6), taken from tbe superior labial gland of 

 Distira cyanocmcta (one of the Hydropbiinae) after secretion, 

 exhibits an alveolus with a lumen enclosed by an epithelium 

 consisting of one layer of cells, and although the proliferating 

 cells are abundantly present, the condition of affairs is more 

 comparable to that found amongst the unicellular glands, no 

 conspicuous disorganization of the mucus-secreting cells having 

 taken place during secretion. Another point of structure is 

 also exhibited by this same figure, viz., that in certain portions 

 of the labial glands of these animals the supporting connective 

 tissue framework is reduced to a minimum. 



The ducts of these glands I have previously considered %, and 

 I find them to be of a much smaller diameter than the measure- 

 ments given by Niemann §. 



Good results were obtained with the following stains : — Hae- 

 matoxylin, Hsemalum, Ehrlich-Biondi, Hsemalum and Safranin, 

 or Dahlia and Eosin. 



The Parotid Gland. — This gland, which is well developed in 

 all families of snakes and which becomes the poison-gland of the 

 venomous species, varies considerably in structure throughout the 

 Ophidia. It is for the most part a serous (albuminous) salivary 

 gland, secreting in the poisonous forms those albumoses|| which 

 appear to be the active agents in snake-poisoning. Its structure in 

 the harmless Colubrine forms is well known, being very similar to 

 that of a mammalian serous gland with more numerous alveolar 

 cells, and it has also been described in the Opisthoglyphous 

 Colubridse^ (in which animals it is often superficially indis- 



* Cfr. Gray's ' Ajiatomy,' 13th edit. 1893, p. 890. 



t These cells are not " destined to supply the place of " the disorganized 

 nmcus-seereting cells, but they give rise by proliferation to others which fulfil 

 this function. 



+ P. Z.S. 1895, pp. 814 & 821. 



§ F. Niemann, " Beitriige zur Morphologic und Physiologie der Oberlippen- 

 drijsen einiger Ophidier," Archiv fiir Naturgeschichte, Bd. i. Heft 3 (Berlin, 

 1892). 



II 0. J. Martin and J. McGrarvie Smith, " The Venom of the Australian Black 

 Snake," Proc. Eoy. Soc. of N. S. Wales, 1892, p. 262. 



^ P. Z. S. 1895, p. 814. 



