60 



Basic Structure of Vertebral! 



ESOPHAGUS LARYNGO- 

 * JrTWM;> TRACHEAL 

 TUBE ~ 

 TRACHEA 



bronchus- 



Fig. 59. Stages in the development of lungs in vertebrates. (A) A frontal section 

 of a salamander embryo showing the series of paired pouches which form the gill- 

 slits. (After Goette.) The last pair of pharyngeal pouches develop into the lungs. 

 Such evidence suggests that lungs may have arisen in phylogenesis from a pair 

 of gill-pouches which failed to reach the surface. (B, C) Earlier and later stages 

 in the development of the lungs in an amphibian. (D) A cross section of the early 

 embryonic lung-sac in a reptile. (After Wiedersheim.) (Bedravvn from lhle. Cour- 

 tesy, Neal and Band: "Chordate Anatomy," Philadelphia, The Blakiston 

 Company.) 



Fig. 60. Laryngeal apparatus of 

 a turtle, Chelone. (ar) Arytenoid; 

 (6 1-2 ) first and second branchial 

 arches; (cr) cricoid; (d) dilator laryn- 

 gis muscle; (g) glottis; (h) hyoid; {he) 

 hyoid cornua; {sph) sphincter laryn- 

 gis; {tr) trachea. Cartilage dotted, 

 bone black. (After Goppert. Courtesy, 

 Kingsley: "Comparative Anatomy 

 of Vertebrates," Philadelphia, The 

 Blakiston Company.) 



