470 



WILLIAM A. LOCY AND OLOF LARSELL 



four moieties to form the single interclavicular sac of the adult 

 are brought out in section 3 of this paper. 



The significant external features of the lung are now estab- 

 lished and subsequent changes show, chiefly, increase in size of 

 the lungs, a relatively larger increase of dimensions of the air- 

 sacs and the development of recurrent bronchi, which on the 

 fifteenth day anastomose with parabronchi. 



, 'Cerv.Sc. 



Ent. 1 -- 

 Ent. 2-- 

 Ent 3-- 

 Ent. 4 - 



Lat.moi. 

 ,-'Rec.Br. 

 Mes.moi. 



A.lnt.Sc. 



Abd.Sc.--\-^ 



Fig. 20 Diagram based on the dissection of the lung of an embryo incubated 

 91 days. Designed to show the lateral and mesial moieties of the interclavicu- 

 lar sac and the connections of air-sacs with the l)ronchial tree. 



Figure 21, a latero-mesial view, shows the relative dimensions 

 of the lung and its air-sacs on the twelfth day of development, 

 There are four well marked indentations of the ribs. The trunks 

 of recurrent bronchi are indicated as developing from the abdomi- 

 nal and posterior intermediate air-sacs, and also from a small 

 accessory sac between them. This accessory sac is apparently 

 cut off from the posterior intermediate and our observations in- 

 cline us to the belief that in this specimen it is connected with 

 the fourth laterobronchus. Schulze ('11) has called attention 

 to it (and its recurrent bronchi) as commonly present in Ciconia, 



