/ 



Poison 



skin appearing perfectly smooth. On the other hand, they may 

 be larger, and if large, are either few and scattered or many and 

 aggregated — the latter condition being illustrated by the warts 

 and parotoids of the toads and by the lateral folds of some of 

 the frogs. 



It is thought that these glands are of two kinds, slime-glands 

 and poison-secreting glands. The slime-glands have for their 

 chief function assistance in the process of respiration by the skin. 

 But it is thought by some that their secretion serves a secondary 

 purpose of protection; that it is an alkaloid and acts as a nar- 

 cotic. The larger poison-secreting glands are sometimes so few 

 and scattered as to be invisible to the naked eye, but often are 

 gathered together in conspicuous elevations. In these aggrega- 

 tions of glands the openings are sometimes plainly visible to the 

 naked eye. (Parotoid glands, Figs. 48 and 89.) The secretion is 

 milky in appearance and acid in character and is ^thought to act 

 as a convulsive.' 



The value of the secretion lies in its protection of the Batra- 

 chian from enemies who would otherwise devour it. This poison 

 is not aseptic, as is the case in poisonous snakes, but acts upon 

 the heart and central nervous system. That of the European 

 toad Bufo vulgaris has been compared to Digitalis and Erythroph- 

 laeum.2 Numerous experiments have proved that toad poison 

 injected into the system will kill any vertebrate, the dose being 

 proportionate to the size of the animal. 



If a young dog takes a toad into its mouth, it will 

 never repeat the act, and perhaps suffers much discomfort for 

 twenty-four hours or more because of this first offence. Snakes 

 eat toads without any apparent discomfort. Skunks are fond 

 of toads as an article of food, but before they eat them they 

 roll them roughly under their paws on grass or other low vege- 

 tation until the poison has been sent out from the glands and 

 rubbed off on the grass. Rana cesopus, the gopher frog of Florida, 

 eats toads, but ejects the poison from the mouth almost imme- 

 diately after swallowing the toad. If the frog is in water, this 

 poison floats at the surface in conspicuous white foamy masses. 



Frogs have less poison in the skin than toads have, and serve 

 as food for all sorts of animals, especially for birds. Herons feed 



1 Physalix, 1890. 

 ^Boulenger, i8g7. 



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