LUNGS OE EEPTILES. 



521 



346 



soon after it has curved over the right pulmonary artery, sends off 

 the trunk of the vertebral and anterior intercostal arteries : in its 

 origin and position, this trunk resembles the common brachial 

 trunk in Lizards. 



The relation of the orio-in of the ri^ht aorta to the ventricular 

 compartment, first receiving the arterialised blood from the 

 pulmonary auricle, and the distribution of the branches of the 

 right aorta, are such, that the head, neck, and fore-limbs receive 

 chiefly arterialised blood, and the abdominal viscera, the trunk, 

 hind-limbs, and tail, are supplied with mixed venous and arterial 

 blood. But this localised distribution of the two kinds of blood 

 is more completely effected in the Cro- 

 codiles, through the modification of the 

 heart and arteries before described. 



§ 92. Lungs of Reptiles. — An opening 

 on the midline of the ventral side of the 

 pharynx, fig. 346, c, receives air introduced 

 into the mouth, and conveys it to the 

 receptacles which, in Reptiles and all 

 higher Vertebrates, are called ' lungs,' ib. 

 f, f. The opening, usually a short longi- 

 tudinal slit, leads, in the Newt and Pro- 

 teus, to a small crescentic membranous 

 sac, from the angles of which are pro- 

 duced the long slender pulmonic bags. In 

 the Axolotl a short tube, strengthened by 

 a few feeble subannular cartilages, con- 

 ducts the air to the lungs, which com- 

 mence just beyond the heart : in the Siren and Land- Salamander 

 a similar trachea divides into two branches, one to each lung. 1 In 

 all these tailed Batrachia the pulmonary bags have simple or even 

 walls. The artery, formed as above described, from the hindmost 

 vascular arch, joined by a branch from the next arch, runs along 

 one side or border, and the vein returns along the opposite border 

 of the lung. The branches proceed from the artery, fig. 348, 

 a, transversely, with regular intervals, midway in which the 

 venules are formed which course half-round the cylinder to open 

 into the longitudinal vein : fibres of elastic tissue accompany the 

 arterioles and venules. The intervening capillaries constitute a 

 regular network, uniformly over the pulmonary surface ; they 

 seem to be mere channels for the passage of the blood discs, fig. 

 347, with intervals or islets of compacted cells, containing nuclei 



xciv. p. 395. 



Respiratory organs, Newt. 



CCXXXVIII. 



