128 HUNriNGTON. 



Before proceeding to details, I may briefly recapitulate the 

 main facts and conclusions which Professor Aeby's work con- 

 tains on the mammalian lung. 



1. Aeby recognizes in each lung a main or '' stem "-bronchus 

 which can be followed caudad and dorsad throughout the entire 

 lung, diminishing in size gradually by giving off lateral branches, 

 capable of being separated into a dorsal and ventral set. Aeby 

 defines this as the monopodic type of division. 



2. The pulmonary artery follows the same general plan of 

 distribution, the main trunk of each side crossing the bronchus 

 ventro-dorsad and continuing caudad on the dorsal aspect of 

 the stem-bronchus, between the ventral and dorsal lateral 

 branches, which are separated from each other by the vessel. 



3. In the human lung and in the lungs of most mammalia 

 the lateral branches on the left side are all given off from the 

 stem-bronchus caudad of the point of intersection of the same with 

 the artery. They constitute, therefore, a group of " Hypar- 

 terial bronchi." On the right side in man and in most mam- 

 malia a bronchus is given off from the stem-bronchus cephalad 

 of its intersection with the pulmonary artery. Aeby distm- 

 guishes this bronchus, which in man supplies the upper lobe of 

 the right lung, as the " Eparterial " bronchus. 



4. Inasmuch as the upper lobe of the left and the middle 

 lobe of the right lung is supplied by the first '' ventral hypar- 

 terial bronchus," Aeby considers them homologous, regarding 

 the '^eparterial" bronchus and its resulting lobe (upper right) 

 as an entirely new structure confined to the right lung, and 

 morphologically not represented on the left side. 



5. While this arrangement obtains in man and most mam- 

 malia, Aeby's researches revealed the fact that certain forms 

 are aberrant in reference to the bronchial and pulmonary vas- 

 cular distribution. 



Aeby classifies the various types determined by himself as 

 follows, the list being completed by the forms examined subse- 

 quently by M. Weber : 



