Introduction 



In the autumn, when the frog or toad feels this slowness and 

 inactivity of the body functions, it creeps away into some pro- 

 tected place or burrows into the soil. (Refer to p. 33.) The 

 burrow is pushed to a greater or less depth, depending on whether 

 the place chosen is at the bottom of a pond, under logs or stones, 

 or in the open earth of gardens or fields — depending also on the 

 species and on the age and consequent size and strength of the 

 individual. 



This hibernation or sleep induced by cold continues until 

 a return of high temperature. If by any cause climatic conditions 

 of the spot chosen should change, or if chance led the batra- 

 chian into a deep well, cave, or other cold situation so that a 

 sufficiently high temperature never returned, hibernation would 

 continue for years perhaps, until, still sleeping, the creatures 

 died from exhaustion of vital forces. Frogs that have been frozen 

 are always found in the hibernating position. 



The Salientia can endure a greater degree of cold than of 

 heat. It is thought that in water death occurs at 40° C. Thus 

 tadpoles and water frogs are often killed in large numbers in 

 the shallow pools of Texas, Land frogs and toads hide away 

 in cooler situations under moss and stones in shaded regions and 

 pass through a period of aestivation till lower temperature re- 

 turns. The tree frogs can endure much higher temperature than 

 can dry-skinned toads or water frogs. It is said that they can 

 sit in the sun at a temperature of 60° C. (120° F.). This is pos- 

 sible because of the moisture secreted by their skins. The fact 

 is that they do not actually experience this high temperature 

 because evaporation keeps the surface cooled to a much lower 

 point. 



VII. The Poisonous Character of Frogs and Toads 



When annoyed or when taken roughly in the hand, mem- 

 bers of the Salientia squirt out from the urinary bladder a trans- 

 parent fluid wholly harmless in character and usually odorless. 

 When handled very roughly by an enemy, a secretion is given 

 out in minute quantities from glands in the skin. This is not 

 harmless if taken into the system of an animal; it is a poison 

 varying in amount and intensity with the species. 



The skin of the Salientia is thickly set with glands. These 

 may be so small that they are invisible to the naked eye, the 



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