HOW THEIR YOUNG ARE BORN. 221 



The Hiss of the Puff Adder. 



It can hiss loudly, and many a man has cause to be grateful 

 that Nature has provided the Puff Adder with that mode of warn- 

 ing its enemies. 



The Puff Adder hisses by drawing air into its sac-like lung 

 and forcing it out rapidly through the glottis and nostrils. These 

 and most other snakes have only one active lung, which is in the 

 form of a long bag with a lining of cellular tissue. 



The Fangs. 

 The dentition of the Puff Adder is elaborate. The poison 

 fangs are long and powerful. Thej^ are hollow, not grooved 

 like those of the Cobra family. Naturally, if such large 

 fangs were fixed solidly in the jaw like those of the Cobra, the 

 snake could not close its mouth. Nature has provided against 

 this, and furnished it with fangs with hinges. The fangs are 

 set in the anterior maxillary bone, which can be moved backwards 

 and forwards like a hinge. So, when the mouth closes, the fangs 

 lie along the sides of the upper jaw, enveloped in a protecting 

 sheath, known as the mucous capsule or vagina dentis. The 

 small teeth in the back part of the upper jaw, and in the lower 

 jaw, are for the purpose of helping to hold the captured prey, and 

 aid in forcing it down the gullet. They are solid and harmless 

 teeth, as far as venom is concerned. To render a Puff Adder 

 harmless the front fangs and the duplicate sets must all be 

 removed, as well as the anterior maxillary bone, otherwise more 

 wall develop in time. 



How their Young are Born. 



Eggs are developed inside the body of the female Puff Adder. 

 These grow full size and incubate within the body. They lie in 

 two long rows on each side of the backbone. Each embryo 

 is enclosed in a thin transparent membraneous sac in which they 

 are born, 'their active struggles, however, soon rupture this 

 sac and they crawl away and lead an existence quite independent 

 of the mother who pays no heed to them. The almost universal 

 belief in South Africa that the young bore their way out of the 

 sides of the parent is untrue. 



