192 



ANIMAL SKETCHES. 



CHAP. 



case. But in the vipers this fang-bearing bone is so 

 hinged to its neighbours that, when the creature is not 

 roused, the poison-tooth can be laid back in the mouth and 

 protected by a fold of skin. Should the creature, how- 

 ever, be enraged, and the niouth be opened widely, its 

 poison-fangs may be separately or simultaneously erected 

 so as to stand out at right angles to the jaw. In the less- 

 developed venomous snakes the curved fang is grooved 

 along its anterior margin; but in the cobras the groove 

 has sunk so deep into the fang that it only opens by a 

 narrow slit, while in the vipers and the ring-hals even 



this slit has closed, 

 an d there is a com- 

 plete canal running 

 from the base of the 

 tooth to a slit-like 

 orifice near, but not 

 quite at the point. 

 Into this canal at 

 its lower end opens 

 the duct of the 



poison-gland, a deadly modification of a harmless salivary 

 gland. In a fair-sized puff-adder I dissected, this was 

 about as large as a bean. About half a drachm of clear 

 gummy poison may be collected from a fresh and vigorous 

 cobra. 



Scarcely less terrible than the venomed fang of the 

 poisonous snakes are the constricting coils of the pythons 

 and boas. We may not now see the snakes fed at our 

 London Zoo ; but the other day at the Antwerp Zoo I 

 watched the pythons at meal-time. It was a painful sight, 

 but most interesting. There were eight or ten snakes ; 

 and about as many pigeons, together with a couple of 

 young rabbits, were introduced. The poor things were 



