A POISONOUS LIZAED. ^ 



we certainly know of one or two cases in which an 

 approach to a poison-apparatus is found. The frogs 

 and toads, " ugly" though they may be, are not yet 

 "venomous/' Shakespeare notwithstanding. Acrid 

 and irritating secretions may be poured out from 

 the skin -glands of these animals. Such secretions 

 are seen typically developed in the toads; but they 

 are not 'poisonous/' in the common sense in which 

 we use that term. 



It is in the class of reptiles that the venomous 

 attains its full development. Here, in the group of 

 the snakes, we reach the acme of poison evolution. 

 A typically poisonous snake, like the rattlesnake or 

 viper, possesses two elongated and hollow "fangs/' 

 borne on its upper jaw. These fangs are merely 

 largely-developed teeth, and their hollow interiors each 

 communicate by means of a canal with the poison 

 gland. This gland, placed in front of and below the 

 eye on each side, is merely a modified salivary gland, 

 and corresponds to that gland in man known as the 

 parotid, and which becomes enlarged in children suf- 

 fering from "mumps." It is highly interesting to 

 find that whilst the poison-secretion of a snake is 

 merely permanently modified saliva, we know of cases 

 among quadrupeds in which the fluid of the mouth 

 becomes temporarily venomous. The case of the 

 rabid dog is. the most familiar example of this fact; 

 and it is curious to reflect on the similarity in nature 

 which exists between the virus of animals so widely 

 separated as are snakes and mammals. 



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