THE EMBRYOLOGY OF THE BIRD's LUNG 39 



Some particulars in which our results differ from those of pre- 

 vious observers may now be mentioned. 



Co77ipariso)i of enibryonic stages. On account of the method 

 employed, of air injection, we were able to carry our studies of the 

 embi-yonic bronchial tree to later stages of development than 

 those previously sketched. One who compares our figures of the 

 embr}' onic tree with those of Juillet will note several discrepancies. 

 The development of the bronchial tree in his reconstruction of the 

 six day stage (his fig. 4) is more advanced than in our sketch of 

 five day twenty hours which is well along in the last half of the 

 sixth day. His reconstruction of the bronchial tree of the eighth 

 day (his fig. 5) is also in advance of our sketches of the same 

 structure in the early part of the ninth day. There is substantial 

 agreement as to the number of main branches but differences in 

 detail including one of importance, viz., the relation of the trans- 

 verse branch of the first entobronchus to the lateral moiety of the 

 subbronchial sac. 



It is also to be noted that Juillet omits the laterobronchi in 

 his reconstruction of the eight day stage. His plastic reconstruc- 

 tion of that stage embraces, besides the mesobronchus, only ento- 

 and ecto-bronchi. In his text, as well as in his sketches, he gives 

 little consideration to the laterobronchi, and sets to one side the 

 dorsobronchi. He states clearly his reasons for so doing. Never- 

 theless, after observing them carefully in embryonic stages as 

 well as in the metalic casts of the adult lung, we are inclined to 

 attach considerable importance to the dorsobronchi, and also to 

 the laterobronchi, on account of the part they play in helping 

 form the network of the bronchial circuits. As Campana pointed 

 out, the dorsobronchi (approximately twenty-five in number) 

 form a fine network in the middle of the dorsal face of the lung 

 that can be detected by surface studied of untreated specimens. 

 The laterobronchi, besides giving rise to an air-sac, form many 

 anastomoses through their branches in the ventral part of the 

 lateral ahd caudal regions of the lungs and also with the recur- 

 rent bronchi of the two posterior air-sacs. 



The interclavicular air-sac. It is on the question of the em- 

 bryonic development of the interclavicular sac that our observa- 



