THE EMBRYOLOGY OF THE BIRD S LUNG 



9 



which two moieties of the interclavicular sac are shown on the 

 left hand of the figure (right lung). The air sacs are all clearly 

 outlined at this stage and the recurrent bronchi have started. 



The air-sacs as shown in figures 47 and 48 are relatively much 

 larger than in the earlier stages. 



Cerv.Sc 



^Rec.Br 



Abd.Sc. 



Fig. 48 Lateral view of the left lung of the .same specimen. Showing the 

 early condition of the recurrent bronchi of the four air-sacs possessing them. 

 The mesial moiety of the interclavicular sac is hidden from view. 



The cervical, the least modified of all the air-sacs, exhibits an 

 expansion of the distal end, but no recurrent bronchi are devel- 

 oped from it. 



The lateral moiety (fig. 47, Lat.moi.) of the interclavicular sac 

 now projects well beyond the lung surface. The beginnings of 

 the recurrent bronchi of this moiety (first seen in the tenth day 

 stage) have elongated and undergone division. They are not 



