164 EEPTILIA. 



the Sauria and Batrachia, while it is divided, and still more dis- 

 tinctly in the Chelonia, into two lobes. A Gall-bladder appears 

 to be always present, and the hepatic and cystic ducts usually pass 

 separately to the intestine ; they are very long and slender in the 

 Serpents ; occasionally, as in Python, several ducts proceed from 

 the gall-bladder, that subdivide themselves into ten tubes, opening 

 each singly into the intestine. Sometimes, as in the Frog, Viper 

 and Crocodile, the two principal ducts unite. 



The Spleen is pretty generally present in the Chelonia, and is of 

 largest size in the Sauria, and, as in the Crocodiles and Tortoises, 

 situate more to the right than left side. The spleen is small and 

 rounded in the Batrachia, and more elongated in the Ichthyodea. 

 It is singularly situated in the Serpents, being, as in Coluber Natrix, 

 firmly attached to the pancreas, and smaller than it in size (though 

 in other Serpents it is larger), and readily distinguished from that 

 gland by its reddish color. 



A Pancreatic gland, more or less developed, is always found ; it 

 is more rarely lobed than simple, and is frequently of a spherical 

 form. It is provided, as in the Chelonia, with a single, or, as in the 

 Crocodiles, with a double excretory duct, while in Python there are 

 several. They enter the small intestine behind the pylorus, accom- 

 panied by, or near to, the gall ducts. In the Serpents the biliary ducts 

 perforate the pancreas. 



ORGANS OF CIRCULATION. 



THE diversities in the arrangement of the Circulatory system in 

 Reptiles are of a very remarkable character, and depend in the 

 Ichthyodea upon the peculiar combination of lungs and gills which 

 they possess, and in the Batrachia, upon the remarkable metamor- 

 phosis that they pass through from their larval, or tadpole mode of 

 respiration by gills, to that by lungs at a later period of existence. 



Those genera of Ichthyodea, as the Axolotl, Proteus, and Siren, 

 which retain during their whole life three tufts of Branchiae, rank 

 nearest to the class of Fishes. The Heart, however, consists in 

 them of a single ventricle, and two auricles (the left the smallest), 

 separated by a delicate septum, and covering with their auricular 

 appendages part of the ventricle and bulb of the aorta. Within 

 the ventricle of the Siren, there is even found a rudimentary sep- 

 tum. The blood, returning from the body, is collected in the large 

 superior and inferior venae cavae, which dilate, as in Fishes, into a 



