THE LIZARD. 173 



precaval (pr.c) passing directly backwards, the postcaval 

 (pt.c) directly forwards into it, while the left precaval (pr.c), 

 on reaching the neck, turns mediamvards and passes across 

 the dorsal wall of the left auricle. 



201. The division of the pulmonary artery as it pierces 

 the front wall of the pericardium into a right and left trunk, 

 each of which passes at first outwards and then backwards 

 to the corresponding lung. 



202. The pulmonary veins (fl.v), bringing the blood 

 from the lungs, and uniting into a short common trunk 

 which enters the left auricle on its dorsal wall. 



r.ao 



duo 



FIG. 44. Lacerta viridis. The aortic arches, supposed to le 

 removed close to thtir origin from the heart (nat. size). 



cr, carotid artery : d.as, dorsal aorta : l.ao, left aortic arch : p.a, pul- 

 monary artery : r.ao, right aortic arch : s.cl, subclavian artery. 



203. Leaving the pericardium, the two aortic arches 

 (Fig. 44) separate from one another, the right arch turning 

 to the right side, the left to the left : traced outwards they 

 are seen to bend round the oesophagus and to unite with one 

 another on the ventral face of the vertebral column to form 

 the dorsal aorta (d.ao). 



204. The carotid arteries (cr), arising together from 

 the right aorta just where it diverges from the left : each 

 carotid passes outwards, parallel with the corresponding 

 aortic arch, with which, at its distal end, it anastomoses 



