11EPTILIA. 



317 



arteries of the kidneys penetrate these organs 

 by their inner margin, whilst the trunks of 

 the emulgent veins occupy the opposite 

 border. These latter are two in number, one 



Fig. 233. 



Generative and Urinary Apparatus of the Rattlesnake 

 (Crotahis Durissus). 



a, the intestines cut off just below the pylorus; b, 

 the gall-bladder: c, the biliary duct, that passes 

 through the middle of the spleen, or, as called by 

 Cams, the pancreas, and enters the large gut ; d, 

 the spleen, or pancreas ; e, the intestines, which 

 were very lai'ge and winding, but short ; ff, the 

 rectum ; h fi, the testes ; i i i, the vasa deferentia ; 

 k k, the penis on each side, which first at the root 

 are conjoined, and are thick beset with bristles ; /, 

 the muscles that serve for drawing in the penis ; 

 m, the scent-bags ; t tt, secretory vessels. 



of which unites with its fellow from the op- 

 posite kidney to form the commencement of 

 the posterior cava. The other communicates 

 with the veins returning the blood from the 

 posterior extremities and the tail ; it is this 

 latter vessel which Mr. Jacobson regards as 

 forming the portal vein of the kidneys.* 



The ureters are longer or shorter in pro- 

 portion as the kidneys are more or less ad- 

 vanced forwards ; they terminate in the 

 cavity of the cloaca, their openings being in the 



* Vide the article Ri.x. 



vicinity of the allantoid sac, if that viscus is 

 present. The allantoid sac, generally called 

 by authors the urinary bladder, in no case 

 immediately receives the terminations of the 

 ureters, and its presence is by no means 

 constant. In the Chelonian order it is very 

 large, and is divided at its fundus into two 

 portions ; but its walls are very thin and 

 membranous. It is likewise met with in the 

 following genera of Saurians ; namely, the 

 Iguana, the Tupinambis, Chameleon, Draco, 

 and Stellio ; while it is wanting in the 

 Crocodiles, Lizards, Agame, Gecko, and other 

 genera of the same order : it is likewise de- 

 ficient in all the Ophidians. The fluid con- 

 tained in this reservoir, when it is present, 

 yields, upon analysis, but very slight traces of 

 urea or uric acid ; so that its claims to be 

 considered as being the real urinary secretion 

 have been doubted, although its urinary 

 character has been admitted by Vauquelin 

 and others. 



In the Chelonian reptiles the urine is a 

 limpid or slightly-coloured fluid ; but in the 

 generality of Saurian reptiles (with the excep- 

 tion of the crocodiles), and likewise in all 

 serpents, it is a white soft substance, which 

 hardens on exposure to the atmosphere into a 

 mass resembling chalk. This solid urine is found 

 on analysis to consist almost entirely of uric 

 acid: it contains besides a very small propor- 

 tion of ammonia of potash and socla in com- 

 bination with uric acid, and also traces of 

 phosphate of lime and animal matter. 



The Emydes among the Chelonian reptiles 

 are furnished with two very remarkable ac- 

 cessory bladders, the size of which exceeds 

 that of the urinary bladder itself; but what is 

 very remarkable, these are met with neither in 

 the land-tortoises nor in the turtles. They 

 are likewise deficient in the genus Trionyx. 

 These accessory bladders are of an oval 

 or cylindrical shape, and are so situated, that 

 they can be compressed by the abdominal 

 muscles. Their walls are extremely delicate, 

 and seem to consist only of an external peri- 

 toneal coat lined with mucous membrane ; no 

 muscular fibres being recognisable in their 

 structure. They are extremely vascular ; the 

 blood-vessels forming a rich net-work over 

 their outer surface. Their use is not yet 

 accurately determined, but it seems probable 

 that the tortoises which exhibit this structure 

 are able to fill the accessory bladders with 

 water and perhaps with air, so as to diminish 

 the specific gravity of their bodies. Should 

 this be the case, it will explain why these 

 organs are deficient in the land tortoises, 

 which never enter the water, and also in 

 turtles, which, from their organisation, are 

 well able to swim without such auxiliaries, 

 more especially as the specific gravity of sea- 

 water is much greater than that of fresh. In 

 the Trionyx, also, the extremities form such 

 powerful oars, that additional means of swim- 

 ming are not required. 



Male Organs of Generation. In all the three 

 orders of reptiles the general arrangement of 

 the generative system of the males is similar 



