THE EMBRYOLOGY OF THE BIRD S LUNG 



457 



do not as 3^et show any buds (fig. 24). Although the differen- 

 tiation of the trachea has begun it is not visible from surface 

 views. Seen from the lateral aspect as in figure 7, the lung 

 pouches, closely united with the walls of the oesophagus, pass 

 below it and unite with the laryngo-tracheal ridge on the ventral 



III IV 



VI 



-Pul.Vn. 



LLg... 



Fig. 5 Dissection of au ink injected chick embryo of 96 hours incubation ex- 

 posing aortic arches and the left lung. Drawn by G. H. A. Rech. 

 ^-■" Figs. 6 and 7 Surface views of the lungs of a chick embryo at the close of the 

 fourth day of development. Figure (5 from the ventral and figure 7 from the 

 lateral aspect. 



