480 WILLIAM A. LOCY AND OLOF LARSELL 



The secondary bronchi, or the originjil branches, from the cen- 

 tral lung tube are designated under four divisions: entobronchi 

 (ventribronchi of Schulze) ; ectobronchi (dorsibronchi of Shulze) ; 

 laterobronchi and dorsobronchi. 



For tertiary bronchi, the terminal branches of the subdivisions 

 of the four kinds of secondary bronchi, we use the term i)ara- 

 bronchi. These are tubes of uniform calibre and unite the dif- 

 ferent systems of bronchi into bronchial circuits. 



In addition to the above, coming from the air-sacs, are the 

 recurrent bronchi of Schulze and Juillet and the air capillaries 

 that are radially arranged around the parabronchi. 



After this digression on the terminology we continue the de- 

 scription of embryonic stages. When the four entobronchi are 

 well started, another series of hernia-like buds arise early on the 

 seventh day. These are the primordia of the ectobronchi and 

 they arise from the wall of the embryonic vestibulum. While in 

 the chick there are usually six, in birds in general they vary 

 from six to ten. It should also be noted in passing, that the four 

 entobronchi enumerated in the chick, may in other birds be as 

 many as six (pelican, Schulze). 



The first ectobronchus springs from the widest part of the em- 

 bryonic vestibulum. By six days six hours it is already of con- 

 siderable length (figs. 30 and 31) and projects forward and 

 slightly laterally. The second, third and fourth ectobronchi are 

 at this stage only papillate buds that protrude dorso-mesially 

 (dorsally in the adult) from the vestibular wall and caudad to 

 the first. 



Figure 31, from a different specimen of the same age as figure 

 30, shows the first ectobronchus in a more favorable position. 



A fifth and sixth ectobronchus are subsequently developed 

 from the wall of the mesobronchus, but further consideration of 

 both ento and ectobronchi will be deferred to a later page. 



Reference to figure 32, which is a sketch of the condition of 

 the bronchial tree in the last half of the seventh day (six days, 

 twenty hours), discloses another series of incipient secondary 

 branches from the central lung tube. These are formed on the 

 lateral wall of the embryonic vestibulum and were called by 



