HUMAN LUNG aot 
A diverging plane of certain branches of the alveolar ducts 
is in definite relation to the next in series. According to Waters, 
in the event of a branch of the bronchial tube dividing twice 
in succession, the diverging plane of the first is perpendicular 
to that of the second. Justesen studied this relation and called 
attention to the fact that the planes sometimes cut each other 
under an angle of 120°. This statement appears to refer to the 
bronchial system and not to alveolar ducts. Now in my model 
the diverging planes of alveolar ducts frequently cross each other, 
but they occasionally lie in the same plane. | 
THE AMERICAN JOURNAL OF ANATOMY, VOL. 27, No. 3 
