20 SPOLIA ZBYLANICA. 



with similar granules elaborated by all the other cells constitute 

 that provision of poison which forms into poison -lakes. 



IV . — Physiology . 



The poison, secreted in the deepest part of the gland, is a 

 very dense and syrupy hquid which, if it is deadly poisonous, 

 would be extremely difficult to inject into a person by the 

 agency of the poison-fang. It is, therefore, indispensable, at 

 the moment of biting, that the poison should be diluted so as 

 to render it more fluid, and consequently more injectable. 

 This task is relegated to the mucous gland situated around the 

 excretory duct. The mucous secretion when poured mto the 

 canal liquefies the poison situated in the forepart of the 

 poison-gland (properly speaking). The latter is replaced by 

 the poison of the lakes which is used for the later l^iting. The 

 powerful muscle which surrovmds the gland mechanically aids 

 in the propelling of the diluted poison, which thus passes into 

 the wound made by the poison-fang. 



To sum up , we see that the jjoison is present in two distinct 

 phases : — 



(1) It is produced as a secretion of the glandular cells and 

 is retained in the reservoirs as a syrupy liquid. 



(2) When the poison is to be utilized a liquefaction of this 

 syrupy substance is effected so that it flows more easily from 

 the gland and penetrates more easily into the bite. 



It is, in one word, a physiological device by which a snake 

 is enabled to keep in a smaU space a large quantity of poison 

 necessary both for its defence and for its ahmentation. 



Explanation of Plates. 



Plate III., Fig. 1. — Section of the whole length of poison 

 gland. X 30. 



(Fixation : Bi-iodide of mercury and formalin stained with 

 Hematoxylin-eosin. ) 



Plate IV., Fig. 2. — Section of parts of four poison lakes with 

 their glandular epithelium. x 100. (Stained with Ironized- 

 hematoxylin.) 



Fig. 3. — Five glandular cells showing the elaboration of 

 poison by cytoplasmic and mitochondrial substances. x 1,100. 

 (Fixation: Regaud's liquid.) 



a = duct. 



6 = poison lake. 



c = glandular epithelium. 



d = fibrous capsule. 



e = poison granules. 



/ = mitochondrial substance. 



g = nucleus. 



h = connective tissue. 



