130 HUNTINGTON. 



Narath establishes the following propositions, based on ex- 

 tensive comparative and human material : 



1. The pulmonary artery in the greater part of its course is 

 i^XdiZ^di later ad of the stem-bronchus, and does not cross the same 

 in Aeby's sense. 



2. The pulmonary artery does not influence the structure of 

 the bronchial tree. 



3. There is no fundamental difference between the *' epar- 

 terial " and *' hyparterial " bronchi of Aeby. 



4. The " eparterial " bronchus is a dorsal (first dorsal) 

 branch, probably originally a lateral branch of the first ventral 

 bronchus shifted upwards on the stem-bronchus. 



5. The right eparterial bronchus (when alone present as in 

 man) is represented by an ''apical" bronchus on the left side, 

 derived as a lateral branch from the first ventral bronchus. 



These important conclusions of Narath will be subsequently 

 again referred to in comparing them with the results obtained 

 by our investigations. 



If we now, carefully and without prejudice, examine a large 

 number of corrosion preparations of mammalian lungs, in which 

 the bronchial system and pulmonary artery have been injected, 

 the following facts w^ill reveal themselves : 



1. A unity of ground plan can be discerned in all, modified in 

 various forms by : 



a. Migration of one or more secondary bronchi cephalad 



on the main bronchus, or even on the trachea. 



b. Corresponding changes in the branching of the pul- 



monary artery. 



c. The appearance, in many forms, of a right accessory 



(cardiac or azygos) bronchus. 



2. If asymmetry exists the right lung is in general the one 

 favored by the greater development and increased calibre and 

 number of the bronchial branches. This physiological pre- 

 cedence of the right over the left lung is characterized by the 

 following facts : 



