REPTILES. 267 



in the lungs. " Hence/' says Professor Bell, "arises the 

 circumstance that these animals have what is called cold 

 Wood; for, as it is from respiration that the blood derives its 

 heat and the temperature of the hody is thereby sustained, in 

 animals which have more perfect respiration, it follows that 

 where this function is but imperfectly performed, the animal 

 heat, muscular force, and all other functions dependent on 

 respiration, will be diminished."* 



In the last class to which our attention was directed that 

 of fishes the circulation throughout life was suited to their 

 residence in water. The first we shall notice in the present 

 class are likewise fitted for aquatic respiration. We shall next 

 proceed to those which in their very early stages breathe by 

 gills, but afterwards by lungs; and thence pass on to those 

 which at all periods possess aerial respiration. 



ORDER I. AMPHIBIA. 



" The swimming Frog, the Toad, the Tadpole, the Wall-Newt, and the 

 water." SHAKSPEARE. 



THE Amphibious Reptiles (order Batrachia\ of Cuvier) may 

 be separated into two divisions those which possess both 

 lungs and gills throughout the entire period of life, and those 

 which have gills in their young state, and acquire lungs as 

 they approach maturity. J The former group possesses some 

 animals of very singular structure and habits ; as the Proteus, 

 which inhabits subterranean lakes in the Tyrol, the Axolotl 



* History of British Reptiles Yan Voorst. Another of that attractive 

 series of works illustrative of the natural history of these countries. In 

 the opinion of the learned author of that work, the structural peculiarities 

 of the Amphibia are such as to justify their being regarded as a distinct 

 class, instead of being merely ranked as one of the orders in Fishes the 

 class Reptilia. Mr. Jennings has thus arranged them in his "Manual." 



f From the Greek word signifying a frog (Lat. Bdtrachus). The term 

 Batrachian means, therefore, a frog-like animal. 



J Those in which the gills are permanent are termed PEREXNIBRAN- 

 CHIATE (Latin, bronchia, the gills, and perennis, permanent, lasting, staying 

 all the year round). Those in which the branchiae disappear, are termed 

 CADUCIBRANCHIATE, the word caducus meaning perishable, falling of 

 itself, &c. 



