LUNGS 



379 



place in addition to the cutaneous respiration common to most 

 Amphibians, in spite of the fact that the skin is especially 

 vascular in these forms. The walls of the mouth, pharynx, and 

 even oesophagus (Desmognathus fusca) are abundantly supplied 

 with capillaries, which may even extend between the epithelial 

 cells. 



Reptiles. In Reptiles, as in all other air-breathing Verte- 

 brates, the form of the lungs is to a great extent regulated by 

 that of the body. In the higher types, such as the Chelonia and 

 Crocodilia, their structure is much more complicated than in 

 Amphibia ; this complication finds expression in a very considerable 

 increase of the respiratory surface. With the exception of the 

 thin-walled lungs of many Lizards, which retain a more primitive 



_- Eli 



FIG. 285. LUNG OF (A), Emy* lutaria (T6 MM. IN LENGTH), AND B, Anyuis 

 fragiiis, BOTH RENDERED TRANSPARENT. (After Fanny Moser. ) 



In A are shown the three large transverse septa (1 3), which separate the 

 lateral chambers, as well as the entrance of the extra-pulmonary bronchus 

 (EH), the first anterior chamber (1 DK), and the posterior chamber (EK). 



condition, more like that seen in the Frog except for the presence 

 of transverse septa, we no longer meet with a large central cavity, 

 but the organ becomes penetrated by a branched system of 

 bronchi connected with a comparatively narrow central bronchus. 



In the simplest condition the trachea opens into the lung 

 by two bronchial apertures, but as the alveolisation of the lung 

 increases, extrapulmonary portions of the bronchi are more 

 marked : they are at first short, but gradually become longer, and 

 each is continued into the corresponding lung as an intrapulmonary 

 bronchus, which may be provided with cartilaginous rings along a 

 considerable part of its course, and which is connected by means 



