350 THE SNAKES OF SOUTH AFRICA. 



suddenly disturbed their slumbers, whereupon both simul- 

 taneously struck fiercely at the intruder. Both missed their 

 aim, and four streams of venom struck one of the plate glass 

 sides of the cage and ran down the glass. The venom, when 

 ejected, is watery, more so than that of the Cobra. 



In the process of collecting venom by forcing a snake to bite 

 over the rubber-covered rim of a watch-glass or wine-glass, the 

 fangs are often erected and remain so, but no venom flows until 

 the glands are compressed with the fingers. 



It was amply demonstrated in this manner that the erection 

 of the fangs did not cause an automatic constriction of the 

 masseter muscle fibres. To eject a full charge of venom, the 

 snake is obliged to grip and compress its head strongly. The jaws 

 of Puff Adders may be extended to their fullest extent yet 

 the fangs are not elevated unless the reptile so desires. I have 

 frequently distended the jaws of Puff Adders and watched them 

 elevate and depress their fangs. The anterior maxillary bones 

 to which the fangs are attached are worked independently of any 

 other parts of the mechanism of the jaws. 



Taking twelve Puff Adders, I made each in turn bite over the 

 thick rim of an ice-cream glass. The instant the rim of the 

 glass touched the snake's nose it bit fiercely, both fangs darting 

 up at the proper striking angle, and then descending with great 

 violence against the inner side of the glass. Each snake was 

 made to bite three or four times. The fangs in each instance 

 would strike the glass and slip upwards towards the rim. Not 

 even the fraction of a drop of venom was shed by five of the 

 snakes. One yielded about three drops, and the rest a very 

 small quantity. From the twelve snakes, I collected seven 

 drops of venom. I tried this experiment several times and found 

 that, although the snake bit the side of the glass freely, either no 

 venom, or only a very small quantity was shed. On the con- 

 trary, when I covered the top of the ice-cream glass with a 

 rather thick piece of sheet rubber, these same Puff Adders in 

 biting through it, shed an average of three to five drops and even 

 ten drops each, into the glass. 



In the former experiments, I was careful to examine the 

 reptiles' mouths to see if venom by any chance had been shed 

 within the mouth, but, with one or two exceptions, there was 

 not a trace of venom to be seen. 



