PRACTICAL MICROSCOPY. 



THE LUNG. 



BRONCHIAL TUBES. 



At the root of each lung the large primary bronchus enters, and 

 immediately divides into two equal branches dichotomously. It is 

 evident that if this mode of subdivision were continued, the peri- 



FIG. 69. DIAGRAM SHOWING THE PLAN OF SUBDIVISION OF BRONCHI, IN THE HUMAN LUNG. 



As the main bronchus enters the organ it is seen to divide, dichotomously, until the resultant 

 branches become quite small say one-tenth inch. These small bronchi now pursue a straight 

 course towards the periphery of the lung, at the same time giving off branches spirally. The 

 last divide dichotomously and result in the terminal, ultimate, or capillary bronchi. 



phery of the organ alone would contain minute bronchi. The arrange- 

 ment is, however, such as to give every wh ere throughout the lung, 



