10 WILLIAM A. LOCY AND OLOF LARSELL 



symmetrically developed, those of the right lung showing more 

 branches. Schulze has pointed out that, after the union of the 

 parts to form a single median sac, there are, commonly, recurrent 

 bronchi only on one side. 



The mesial moiety {Mes.moi.) of the interclavicular sac is 

 forked at its extremity into two lobe-like branches, the more 

 mesial of which extends towards the median plane and comes 

 nearly into contact with the corresponding branch from the op- 

 posite lung. The laterally extending branch, passes ventral to 

 the extra pulmonary bronchus, and partly engirdles the bronchus 

 on the left hand of the figure. 



The anterior intermediate air-sac {A.int.Sc.) has increased in 

 size and its recurrent bronchi are much further developed. They 

 occupy the antero-lateral border very close to those of the lateral 

 moiety of the interclavicular sac. 



Figure 47 shows also the connection between the mesial moiety 

 of the interclavicular, and the anterior intermediate — both aris- 

 ing on a common canal (interclavicular canal) that opens into 

 the third entobronchus (entobronchus not shown) . 



The posterior intermediate and abdominal air-sacs lie at the 

 caudal extremity of the lung and have obviously increased in 

 size. In figure 47, only the proximal ends of the recurrent bron- 

 chi have been sketched since these show on the surface. They 

 exhibit the same relationships as in the tenth day stages. 



Figure 48, which is a dorso-lateral view of the same specimen 

 shows to greater advantage the recurrent bronchi from the lat- 

 eral moiety and the anterior intermediate air-sac at ten and one- 

 half days. The specimen in this position also shows the recur- 

 rent bronchi from the posterior intermediate and abdominal sacs. 

 The enlargement at the base of the recurrent bronchi well exhib- 

 ited in the posterior intermediate jjrobably corresponds to the 

 basal pocket of Schulze. 



Although the general appearance of the air-sacs on the tenth 

 day of development (figs. 36 and 37) have been described, it will 

 be advantageous for comparison to insert at this point a separate 

 sketch of the anterior intermediate air-sac and the mesial moiety 

 of the interclavicular sac. Figure 49 represents these air-sacs as 



