424 



COLLEGE ZOOLOGY 



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Figure 297. The ringhals, a South African cobra {Hemachatus haemachatus) , with its neck 

 spread, ready to strike and inject venom which may cause death in a few minutes. (Courtesy of 

 American Museum of Natural Histon,'.) 



Florida and west to Texas. An average speci- 

 men measures about IVz feet. 



The rattlesnake (Fig. 301) is easily dis- 

 tinguished by the rattle at the end of the 

 tail in the adult. This consists of a number 

 or horny, bell-shaped segments loosely held 

 together. Before striking, the rattlesnake 

 often vibrates the end of the tail rapidly, 

 producing a sort of buzzing noise, which to 

 the wise serves as a warning. The venom is 



secreted by a pair of glands on each side 

 of the head above the jaws (Fig. 288) . These 

 glands open by venom ducts into the fangs. 

 The poison fangs are pierced by a canal 

 which opens near the end. The venom 

 glands are surrounded by muscles that con- 

 tract to squeeze the poison out of them 

 through the fangs and into the animal 

 bitten. There are several small fangs lying 

 just behind the functional ones; these are 



