UKINARY APPARATUS. 711 



(2010.) The urinary excretion in Reptiles becomes of very consider- 

 able importance, and the structure of the kidneys and excretory ducts 

 proportionately elaborate. The kidneys (fig. 353, o, p) are generally 

 situated very far back, even within the cavity of the pelvis where a 

 sacrum exists, as in the Chelonian and Saurian orders ; and in these 

 tribes they are very partially covered by the peritoneum, being firmly 

 imbedded in the sacral region. But in the Serpents, in consequence of 

 the elongated form of the body and the complete flexibility of every por- 

 tion of the spine, the kidneys are peculiar both in their position and 

 general structure. Instead of being placed upon the same level as in 

 other Yertebrata, the right kidney of an Ophidian is situated much 

 more anteriorly than the left, a circumstance which much facilitates 

 the packing of the abdominal viscera, and contributes greatly to ensure 

 the free movements of the vertebral column at this place. For the same 

 reason, the kidneys of a Serpent are divided into numerous lobes, placed 

 in a longitudinal series upon the outer side of the commencement of the 

 ureter, and loosely connected to each other and to the spine by cellular 

 tissue and a fold of the peritoneum. 



(2011.) As relates to the minute structure of the kidneys in the 

 Reptilia, these viscera are invariably composed of convoluted tubes, 

 which pour their secretion into the commencement of the corresponding 

 ureter. The ureters, of course, vary in length according to the position 

 of the renal organs ; they ultimately terminate in the cloaca (fig. 353, u) 

 a cavity or general outlet through which, in the female, the ova, the 

 faeces, and the urine are discharged, and which in the male gives passage 

 to the contents of the rectum, the secretion of the kidneys, and the 

 semen. 



(2012.) In connexion with the urinary apparatus of Reptiles, it will 

 be convenient to mention a bladder that exists in Chelonian and Am- 

 phibious reptiles, and is also found in some Saurian tribes, to which the 

 name " urinary bladder " has been erroneously applied. This bladder, 

 in the Tortoise (fig. 353, A) and Proteus (fig. 340, q), is of considerable 

 size, and in the Frog forms a very capacious receptacle, having its upper 

 part divided into two cornua. It is generally filled with a clear limpid 

 fluid, which in the case of the Frog is forcibly ejected if the animal be 

 alarmed ; but that this fluid is not urine is obvious from the fact already 

 stated, that the ureters open into the cloaca (fig. 353, u), and not into 

 the bag referred to ; the latter, in fact, is the unobliterated remains of 

 the allantois of the embryo, concerning which further particulars will 

 be given in the next chapter, and the fluid contained in it is most pro- 

 bably the product of cutaneous absorption*. 



(2013.) In tracing the development of the generative apparatus 

 through the different orders of Reptiles, the student will not fail to ob- 

 serve many beautiful illustrations of progressive improvement. 



* Vide Cyclopedia of Anatomy and Physiology, art. AMPHIBIA, by Professor 

 Bell, p. 104. 



