493 



illustrated in Fig. 8, the union and disappearance of the septum is 

 completed by the close of the first day after hatching. 



Having followed the history of t4ie recurrent bronchi from their 

 earliest appearance to the time when they have established their 

 characteristic connections with other parts of the bronchial tree, they 

 should now be described in the adult lung. 



Attention should be first called to Campana's ('75) analysis of the 

 orifices into the air-sacs. He makes of these two groups, the mono- 

 bronchial and the polybronchial, according to the number of openings 

 which they exhibit. Juillet ('11) further distinguished them as (1) 

 direct orifices and (2) recurrent orifices. 



According to this analysis, which is in harmony with the devel- 

 opmental history, the prebronchial sac has a direct monopodial orifice 

 only, since it does not possess recurrent bronchi. A number of branches 

 of the first entobronchus extend posteriorly into the lung from a point 

 nearly opposite the direct orifice of the prebronchial sac. These possibly 

 serve the same function as the recurrent bronchi of the other air 

 sacs, but do not appear to be developed from the sac itself as are the 

 tubes which have been called recurrent bronchi. 



The sub-bronchial air-sac has two groups of orifices into each 

 lung. The more mesial orifice, which is of the monobronchial direct 

 type opens into a short tube, already described, into which the direct 

 orifice of the anterior intermediate sac also opens. This short tube in 

 turn communicates with the third entobronchus. 



The more lateral group of sub-bronchial orifices is polybronchial 

 and has both a direct and several recurrent orifices. The direct orifice 

 is the opening of the ventral tip of the first entobronchus, from which 

 as already described the lateral moiety of this sac has its origin. The 

 recurrent orifices are three or four in number, and are the proximal 

 openings of the recurrent bronchi. Reference to fig. 6 will show 

 that on the eleventh day of incubation there were but two recurrent 

 openings into this sac. The change to the adult condition is brought 

 about by the expansion of the proximal ends of the original recurrent 

 bronchial buds to form a part of the air-sac. The primary branches 

 of the original recurrent bronchi in this way are made to open directly 

 into the air-sac. 



The distal ends of the sub-bronchial recurrent bronchi anastomose 

 chiefly with the more ventral branches of the first ectobronchus. 



