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 Botallit to the carotid arch of the right side, and then 
curves round the heart to join the left arch, the two thus 
2 av 
Tic. 342.—Heart and associated vessels of a lizard. 
—After Nuhn. 
A., Right auricle; jugulars (/.), subclavians (Sc.v.), and inferior 
vena cava (/.V.C.) enter it, V., ventricle; ¢., truncus arteri- 
osus ; 1, first aortic arch giving off carotids; 2, second aortic 
arch; Z.a., pulmonary artery; Sc.a., subclavian artery ; Ao., 
dorsal aorta. A.1, left auricle; pulmonary veins (4,.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 cceliaco- 
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- 
