452 



MANUAL OF ZOOLOGY 



SECT. 



aperture (za\ and injected into the wound made by the 

 fang. The effect is to produce acute pain with increasing 

 lethargy and weakness, and in the case of the venom 

 of some kinds of Snakes, paralysis. According to the 

 relative amount of the poison injected and the degree 

 of its virulence (which differs not only in different kinds 

 of Snakes, but in the same Snake under different con- 

 ditions) the symptoms may result in death, or the bitten 

 animal may recover. The poison is a clear, slightly straw- 

 coloured or greenish liquid ; it preserves its venomous 



FIG. 256. Poison apparatus of Rattlesnake. A. eye; Gc. poison-duct entering 

 the poison-fang at t 5 Km. muscles of mastication partly cut through at * ; Me. 

 constrictor muscle ; Me', continuation of the constrictor muscle to the lower jaw ; 

 N. nasal opening ; 6". fibrous poison-sac ; z. tongue ; za. opening of the poison- 

 duct ; zf. pouch of mucous membrane enclosing the poison-fangs. (From 

 Wiedersheim.) 



properties for an indefinite period, even if completely 

 desiccated. The poisonous principles are certain proteids 

 not to be distinguished chemically from other proteids 

 which have no such poisonous properties. Immunity 

 against the effects of the poison, and relief of the symptoms 

 after a bite has been inflicted, have been found to be con- 

 ferred by injections of the serum of animals which have 

 been treated with injections of increasing doses of the 

 poison. 



