174 REPTILIA. 



URINARY ORGANS. 



ALL Reptiles are provided with Kidneys, which are commonly 

 situated far backward and deeply within the pelvis. In the 

 Anourous Batrachia, however, and especially in the Ophidia, they 

 are placed far forward, and in the latter order the right kidney lies 

 asymmetrically in relation to the left, being placed higher up and 

 in advance thereof. The size of these organs varies in the several 

 orders, but is generally very considerable ; they are very narrow, 

 elongated, and run to a point anteriorly in the Ichthyodea and 

 Tailed Batrachia ; of an elongato-oval form with slight incisures 

 in the Lizards and Anourous Batrachia ; in the Ophidia they are 

 for the most part very elongated and flat, and divided into round 

 lobules, while in others, e. g., Boa, they are portioned out into narrow 

 plates lying one upon the other; in the Crocodiles and Chelonia 

 they are broader, and frequently, especially upon the posterior part, 

 provided with indentations. Occasionally, as in the Rattle-Snakes, 

 each kidney is completely divided into an upper and under piece. 

 In rare cases both kidneys, as in Lacerta ocellata, appear to coalesce 

 inferiorly into one entire mass, a structure of which we are 

 reminded in several Fishes and Birds, and occasionally in its very 

 interesting occurrence as abnormal in Man, where it is due to an 

 arrest of development. As regards the more minute structure of 

 the kidneys, we may perceive in their early conditions in the Ba- 

 trachia and Ichthyodea, narrow coecal canals supported upon the 

 extremity of the ureter, and in the Ophidia these, which are much 

 longer and more contorted, unite together in a racemiform manner, 

 and give off at intervals small trunks into the ureter ; even in the 

 more compact substance of the kidneys in the Chelonia and Sauria, 

 the blindly terminating ccecal canals are found to be continuous 

 from the peripheral to the middle part of the organ, with ramifica- 

 tions of the ureter. The kidneys, as has been already stated, have 

 a special portal system. The afferent veins form, e. g., in the Frog, 

 a couple of small trunks which enter the kidney inferiorly and 

 externally, and are distributed upon its posterior surface. The 

 efferent veins take their origin by radicles from the anterior surface, 

 and pass to the inferior vena cava. The ureters are mostly short 

 and delicate, situated usually upon the internal inferior edge of the 

 kidney, and in the Ophidia attain no inconsiderable length ; they 

 perforate the walls of the posterior region of the cloaca, discharging 



