348 



MANUAL OF ZOOLOGY 



of cartilage. The trachea bifurcates when it enters the 

 body-cavity, each of the two branches, or bronchi as they 



are termed, passing to the 

 corresponding lung. In the 

 lizard the lung is in essence 

 a thin-walled sac with elas- 

 tic walls. In the wall of 

 the sac immediately out- 

 side, the delicate internal 

 epithelium is a rich net- 

 ■£jf work of blood-vessels, into 

 the blood contained in 

 which oxygen from the air 

 in the cavity of the lung 

 readily passes, while the 

 carbonic acid is at the 

 same time given off. In 

 the rabbit the lung is of 

 much more complicated 

 structure, but the essential 

 relations are the same. 



In the lizard the lungs 

 lie in the anterior part of 

 the general body-cavity. 

 In the rabbit the anterior 

 part of the body-cavity, 

 containing the lungs and 

 the heart, is separated off 

 from the posterior part, 

 containing the greater por- 

 tion of the enteric canal and 

 other organs, by a muscular 

 partition concave posteri- 



Fig. 217. — Lacerta agilis. General view 

 of the viscera in their natural relations. 

 Bl, urinary bladder; Ct, post-caval vein; 

 ED, rectum; GB, gall-bladder; H, 

 heart; Lg t Lg ', the lungs; M, stomach; 

 MD, small intestine; Oe, oesophagus; 

 Pn, pancreas; Tr, trachea. (After 

 Wiedersheim.) 



