REPTILIA. 



preserve these organs, even after the development of their 

 lungs. In several oviparous reptiles, the Colubers particu- 

 larly, the young animal in the egg is formed and considerably 

 advanced at the moment of its exit from the mother ; and there 

 are even some species which may be rendered viviparous by 

 simply retarding that epoch. (1) 



The quantity of respiration in Reptiles is not fixed like that 

 of the Mammalia and Birds, but varies with the proportion of 

 the diameter of the pulmonary artery compared to that of the 

 aorta. Thus Tortoises and Lizards respire more than Frogs, 

 &c.j and hence a much greater difference of sensibility and 

 energy than can exist between one of the Mammalia and ano- 

 ther, or between Birds. 



Reptiles accordingly present an infinitely greater variety of 

 forms, motions, and properties than are to be found in the two 

 preceding classes, and it is in their production that Nature 

 seems to have amused herself by imagining the most fantastic 

 shapes, and by modifying in every possible way the general 

 plan she has followed in the construction of the Vertebrated 

 animals, and in the Oviparous classes especially. 



The comparison, however, of their quantity of respiration 

 and of their organs of motion, has enabled M. Brogniart to 

 divide them into four orders, (2) viz. 



The Chelonia, or Tortoises, whose heart has two auri- 

 cles, and whose body, supported by four feet, is enveloped by 

 two plates or bucklers formed by tbe ribs and sternum. 



The Sauria, or Lt2Jards, whose heart has two auricles, 

 and whose body, supported by four or two feet, is covered 

 with scales. 



The Ophidia, or Serpents, whose heart has two auricles, 

 and whose body always remains deprived of feet. 



The Batrachia, whose heart has but one auricle, and 

 whose body is naked, most of which pass, with age, from the 



(1) The Colubers, for instance, when depinved of water, as proved b\' the ex- 

 periments of M. Geoffrey. 



(2) Al. Brogniart, Essai d'une Classification Naturelle des Reptiles, Paris, 1805, 

 and in the M^m. des Savants Etrang., torn. 1, p. 587. 



