RESPIRATORY SYSTEM. 627 



limbs and kidneys, and finally, at the posterior end of the kidneys, 

 reunite to form the caudal artery, which runs down the tail. 



The blood from the anterior region of the body is returned to the 

 heart by the right and left precaval veins or superior venae cavse. The 

 right precaval is formed by the junction of external and internal 

 jugulars with the subclavian vein ; on the left side the jugular is absent. 

 From the posterior region of the body, blood is brought back by the 

 postcaval vein or inferior vena cava. The three great veins open into a 

 thin-walled sinus venosus, which opens into the right auricle. 



The postcaval is formed by the union of two veins which run along 

 the genital organs, and receive renal veins from the kidneys. In pass- 

 ing through the liver the postcaval receives important hepatic veins. 



From the tail region the blood is brought back by a caudal, which 

 bifurcates in the region of the kidneys into two pelvics. The pelvic 

 veins give off renal-portals to the kidneys, and receive the femoral and 

 sciatic veins from the hind-limbs. They then unite to form the 





FIG, 343. Lung of Chamaleo vulgaris^ showing ah -sacs. 

 After Wiedersheim. 



epigastric or anterior abdominal, which carries blood to the liver. 

 Except through the medium of the renal-portal system, there is no 

 connection between the anterior abdominal and the postcaval. To the 

 liver, blood is carried as usual from the stomach, etc., by the portal 



in. 



From the lungs blood is brought to the left auricle by the pulmonary 



ins. 



There is, as usual, a lymphatic system, including a pair of lymph hearts. 



Respiratory system. The lungs are elongated oval 

 structures which taper away posteriorly. The mouth does 

 not, as in the frog, play an important part in the respiratory 

 movements. In some lizards (Chamaeleon and Geckos) the 

 lungs are prolonged in air-sacs, suggesting those of Birds 

 (Fig. 343). 



Excretory system. The paired kidneys lie in the 

 extreme posterior region of the abdominal cavity, and 



vein. 

 Fr 

 veins. 



