495 



adult lung) three or four in number, are the openings of the recurrent 

 bronchi and have a history very similar to that already described in 

 connection with the two preceding sacs. The anterior ends of the 

 posterior intermediate recurrent bronchi have for the most part anastom- 

 osed with the first and second laterobronchi. 



The abdominal air-sac orifices are also of two kinds, direct and 

 recurrent, and are so arranged as to form a polybronchial group. The 

 direct orifice (fig. 8 and 9, d.o.) is the opening of the mesobronchus 

 into the sac. The recurrent orifices (fig. 8 and 9, o.) are again the 

 result of expansion of the original main recurrent bronchial trunk to 

 form this proximal part of the air-sac in such a manner that its 

 branches open directly into the adult sac. The recurrent orifices are 

 four or five in number. The 

 recurrent bronchi of the abdo- 

 minal sac by their anastomoses 

 form an important part of the 

 lateral lung facet. 



Fig. 10 shows the relation 

 in the adult of the recurrent 

 bronchi of the abdominal and 

 anterior intermediate air-sacs to 

 the bronchial- tree and the way 

 in which their stems connect 

 with the air- sacs. In this cast 

 the abdominal air-sac was only 

 parthy injected so that the 

 proximal end alone is shown. 

 It will be seen that the main 

 recurrent bronchi of the abdomi- 

 nal air-sac (ab.) extend more 

 than one-third of the way toward 



the ventral anterior border of the lung before branching to any marked 

 extent. The rami into which these recurrent bronchi finally break up 

 however, anastomose, as previously indicated, with the numerous air- 

 passages in the lateral facet of the lung. 



Summary. 

 1. The recurrent bronchi are outgrowths from the air-sacs, and 

 the air-sacs in turn, except the abdominal, are the expanded terminal 



Fig. 10. Photograph of Wood's metal 

 cast of lung of small adult domestic fowl, 

 seen from the lateral aspect, showing the 

 anterior and posterior intermediate air-sacs 

 expanded, and a portiou of the abdominal 

 air-sac. 



The recurrent bronchi of the anterior 

 intermediate and abdominal air-sacs have 

 been blackened with ink in order to diflFe- 

 rentiate them in the figure more clearly. 



