626 REPTILIA. 



the more ventral part arises the left aortic arch, which 

 curves round to the left side, first giving off a short connect- 

 ing vessel (ductus Botallii) to the carotid arch. From the 

 other division of the truncus arteriosus, a great arterial 

 trunk arises, and this gives off the right aortic arch and the 

 right and left carotid arches. The right aortic arch sends a 

 ductus Botallii to the carotid arch of the right side, and then 

 curves round the heart to join the left arch, the two thus 



FlG. 342. Heart and associated vessels of a lizard. 

 After Nuhn. 



A., Right auricle; jugulars (/.), subclavians (Sc.v.), and inferior 

 vena cava (I.V.C.) enter it. V., ventricle ; tr. t truncus arteri- 

 osus ; i, first aortic arch giving off carotids ; 2, second aortic 

 arch ;/.., pulmonary artery ; Sc.a., subclavian artery ; Ao. t 

 dorsal aorta. A.' 1 , left auricle ; pulmonary veins (p.v.) enter 

 it. In the lizard described, the left jugular is not developed. 



forming the dorsal aorta. The carotid arches supply the head 

 region with blood. From the base of the truncus arteriosus, 

 the right and left pulmonary arteries also arise (Fig. 342). 



From the right aortic arch as it curves round, arise the right and left 

 subclavian arteries, which carry blood to the fore-limbs. A coeliaco- 

 mesenteric artery arises from the dorsal aorta and supplies the viscera. 

 Smaller vessels are also given off to the genital organs, etc., and then at 

 the anterior end of the kidneys the aorta divides into two femoral 

 arteries, which break up into a network of small vessels, supplying hind 



