SAXGUIFEROUS SYSTEM. 487 



intercostal arteries of the posterior part of the body are derived 

 from the common trunk of the abdominal aorta, formed by 

 the early anastomosis of the left with the right aortic arch, 

 and from the length of the abdominal viscera and their dis- 

 tance from each other, these organs are supplied by distinct 

 hepatic, gastric, mesenteric, and genital arteries, which 

 come off, not from a common creliac or visceral artery, but 

 successively and directly from the long trunk of the posterior 

 aorta in its course backwards under the vertebral column. 



The venous blood is returned from the head by two jugu- 

 lar veins, and from the intercostal spaces by two azygous 

 branches which unite before entering the right auricle. The 

 caudal veins returning the blood from the posterior parts 

 of the body appear to distribute a portion through the kid- 

 neys, like the renal portal circulation of fishes, and to 

 convey another portion to the mesenteric vein, to be sent 

 with the venous portal circulation through the liver. The 

 spermatic veins pass with the efferent renal veins into the 

 posterior vena cava, to be sent with the venous blood of 

 the superior cava and hepatic vein into the right auricle and 

 right cavity of the ventricle, and thence by one or two pul- 

 monary arteries through the single or double respiratory 

 sac. 



The exterior surface of the ventricle in the saurians is 

 more generally connected with the interior of the pericardium 

 by tendinous threads than in the ophidian reptiles ; more 

 than twelve of these connecting filaments, most numerous in 

 the invertebrata, are found in the pseudopus, two in the mo- 

 nitors, and one or more in the crocodiles and most other 

 genera. I have found eight of these tendinous bands, arising 

 by separate peduncles, near the apex of the ventricle, in the 

 adult heart of the large gavial of India, where the pericardium 

 is nearly a line in thickness, white, fibrous, and of great 

 strength. The general structure of the heart and the distri- 

 bution of the great central blood vessels are nearly the same 

 in the lacertine sauria as in the ophidian reptiles. The peri- 

 cardium is generally stronger, the auricles more muscular, 

 short, and lobed at the margin, the ventricle with thicker 

 parietes, and the septum more developed between its 

 compartments ; the great pulmonic and systemic trunks are 

 bound together by condensed cellular substance and by the 



