28o 



COMPARATIVE MORPHOLOGY OF VERTEBRATES 



of shape than do the lungs in other groups. Their structure is pecu- 

 liar. Each bronchus enters the medio ventral side of the correspond- 



FiG. 304. — Diagrammatic side view of bird lung, showing the parabronchl connect- 

 ing ecto- and entobronchi, after Locy and Larsell. b, bronchus; ec, ectobronchi; en, 

 entobronchii, 0, abdominal orifice, point of connexion with abdominal air sac; p, para- 

 bronchi; r, impressions of ribs. 



ing lung and immediately enlarges into a vestibule or atrium (not 

 shown in fig. 303), beyond which it continues as a main trunk, the 

 mesobronchus, to the distal end of 

 the lung. From this mesobronchus 

 secondary bronchi arise, these being 

 called entobronchi, ectobronchi, 

 laterobronchi and dorsibronchi, ac- 

 cording to their position. These 

 secondary bronchi divide and give off 



Fig. 305. Fig. 306. 



Fig. 305. — Section of lung pipe with radiating infundibula, after Schulze. 



Fig. 306. — Ventral view of lungs and air sacs of twelve-day chick embryo, after 

 Locy and Larsell. ai, anterior intermediate sac, a, abdominal sac; c, cervical sac; /, 

 lateral moiety of interclavicular sac; lu, lung; m, mesial moiety of interclavicular sac; 

 oe, oesophagus; p, posterior sac; t, trachea. 



small tubes of uniform diameter — the air pipes or parabronchi (fig. 

 304) — which connect at the other end with others of the secondary 



