POISON APPARATUS. 343 



jaw in the bone known as the anterior maxillary. All this class 

 are venomous. They are known as the Proteroglypha, which 

 means snakes with the anterior (front) maxillary teeth grooved 

 or hollow. The Viperine snakes are more correctly known as 

 the Solenoglypha. 



Result of Investigation. 



Our well-known Boomslang or Tree Snake [Dispholidus typus) 

 is a member of the Opisthoglypha or Hind-fangcd Snakes, which 

 is generally believed to be at most very slightly venomous — only 

 sufficiently so to enable it to paralyse its prey before deglutition. 



The reasons for this belief are based on the fact of the snakes 

 of this class possessing imperfectly developed poison glands 

 which are not connected with the grooved teeth by well-defined 

 poison ducts, as is the case with the typical venomous snakes ; 

 hence they are wrongly considered to be in a more or less rudi- 

 mentary or transition stage. 



The results of the experiments with the Boomslang, given in 

 detail in a former chapter, have, I think, conclusively shown 

 that one member at least of this class of so-called slightly venom- 

 ous snakes is as highly venomous as the Cape Cobra or Puff 

 Adder. It is reasonable, therefore, to assume a good many of 

 the others would, on investigation, be found to be equally 

 venomous. Therefore, until each individual of this large division 

 of snakes has been carefully experimented with, it would be unwise 

 to lead the public to infer they were either practically harmless 

 or only slightly venomous. In South Africa we have twenty-six 

 species of these Hind-fanged Snakes so far recorded. 



Poison Apparatus. 



The venom of snakes is secreted by a pair of glands lying on 

 each side of the skull beneath the skin, situated just under and 

 behind the eyes. The Night Adder {Causus rhombeatus) is an 

 exception to this rule. The venom glands are almond-shaped, 

 and are composed of great numbers of cells. Within the glands 

 are cavities known as Alveoli. These are lined with short 

 columnar cells. In these cavities the venom is stored until 

 squeezed out by the contraction of the gland by certain muscles, 

 masseters, temporals, and pterygoids. The glands are termed 



