42 WILLIAM A. LOCY AND OLOF LARSELL 



Excepting the analysis of Campana and of Juillet, there is 

 much confusion among authors regarding the orifices of the air- 

 sacs. In the chick we find seven groups of orifices, agreeing 

 with Juillet except in regard to the nature of the lateral orifice of 

 the interclavicular sac. This we find to be mixed polybronchial 

 instead of simple polybronchial as claimed by Juillet. On the 

 basis of our observations the seven groups of orifices are : one di- 

 rect monobronchial orifice for the cervical sac; one medial direct 

 monobronchial, and one, laterally placed, mixed polybronchial 

 for the interclavicular sac, one direct monobronchial and one 

 simple i^olybronchial for the anterior intermediate sac ; one mixed 

 polybronchial for the posterior intermediate and one mixed 

 polybronchial for the abdominal sac. 



As Juillet ('12) has shown in admirable comparative studies, 

 much variation exists as to numbers (6 to 9) and arrangement of 

 orifices in the twenty-five species of birds which he studied. 

 Since our observations are limited to the chick, the reader is re- 

 ferred to Juillet 's analysis of the different types of orifices (pp. 

 340-351) which can not be satisfactorily abbreviated. 



As regards the method of growth and the type of branching 

 within the lungs, we shall limit ourselves to the brief remarks — 

 that the excellent observations of jMoser indicate the general 

 method of growth and on the ciuestion of branching by mono- 

 podial or dichotomous formation, our observations incline us to 

 adopt the view of an unequal dichotomy. 



Recurrent hronchi. The recurrent bronchi are the most im- 

 portant recently recognized structures connected with the lungs 

 of birds. As already indicated the credit for the recognition of 

 their structure, development and physiological function is shared 

 by Schulze ('11) and Juillet ('12). These new structures are of 

 especial interest. There is no doubt that they spring from the 

 air-sacs and grow into the lungs where they establish numerous 

 connections with the bronchial branches. This gives a new view 

 of air sacs: They are expanded parts of the bronchial circuits; 

 branches from the main bronchus lead into them, but they are not 

 terminal sacs, they are air reservoirs on the course of the bron- 



