AMPHIBIANS 2625 



In the economy of Amphibians the naked skin and its glands play a most im- 

 portant part, since none of them drink, in the proper sense of the word, but imbibe 

 moisture through the pores of their integument. Moisture is, indeed, essential to 

 their existence, and if they be confined in a dry atmosphere they soon perish. It is 

 true that frogs may be seen basking in the sun's rays, and apparently enjoying the 

 warmth as much as lizards, but they only do this in the neighborhood of water, to 

 which they retire when necessary. Such members of the class as inhabit dry locali- 

 ties, are mostly nocturnal, avoiding sunshine, and wandering abroad when they can 

 obtain moisture from dew. 



The skeleton of the Amphibians presents many peculiarities, and in 



some forms has numerous fish-like characteristics. For instance, in 



certain of the forms with permanent gills the vertebrae are scarcely distinguishable 



from those of fishes; whereas in the true newts they have a rounded knob at the 



front of the body and cup at the hinder extremity, and are closely articulated with 



SKELETON OF SALAMANDER. 



one another. In the long-tailed groups the number of vertebrae is considerable; 

 but in the frogs and toads those of the back are reduced to seven or eight, the 

 hinder end of the backbone terminating in a long style extending between the 

 greatly produced extremities of the haunch bones, or ilia, which articulate with the 

 lateral processes of the sacral vertebrae. The transverse processes of all the 

 vertebrae are well developed, and in some cases very long; and they take the place 

 of ribs, which, at the most, are represented by some small rudiments. In conse- 

 quence of this absence of ribs, Amphibians are unable to breathe in the ordinary 

 way by alternate expansion and contraction of the cavity of the chest, and they, so 

 to speak, swallow air, taking in a large gulp, and then closing the mouth. In 

 addition to the peculiarities connected with its condyles and the basioccipital region 

 the skull is distinguished by its flattened, broad, and more or less semicircular 

 form; the sockets for the eyes being generally large and ill-defined. In front of 

 the condyles the under surface of the middle of the skull is overlain by a 

 large parasphenoid bone, which is frequently dagger shaped; this bone being 

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