274 RESPIRATION 



ference. The vesicles of adjacent lobules do not communicate. Those of 

 the same lobule or proceeding from the same intercellular passage com- 

 municate, as a general rule, only near angles of bifurcation, so that when any 

 bronchial tube is closed or obstructed the supply of air is lost for all the blood 

 vessels of that lobule and its branches. 



Blood Supply. The lungs receive blood from two sources: 0, the 

 pulmonary artery; b, the bronchial arteries. The former conveys venous 

 blood to the lungs for its oxidation, and this blood takes no share in the 



FIG. 226. Section of Injected Lung, Including Several Contiguous Alveoli. (F. E. 

 Schulze.) Highly magnified, a, a, Free edges of alveoli; c, c, partitions between neighbor- 

 ing alveoli, seen in section; b, small arterial branch giving off capillaries to the alveoli. 

 The looping of the vessels to either side of the partitions is well exhibited. Between the 

 capillaries is seen the homogeneous alveolar wall with nuclei of connective-tissue corpuscles 

 and elastic fibers. 



nutrition of the deeper pulmonary tissues through which it passes. The 

 branches of the bronchial arteries are nutrient arteries which ramify in the 

 walls of the bronchi, in the walls of the larger pulmonary vessels, and in the 

 interlobular connective tissue, etc. The blood of the bronchial vessels is re- 

 turned chiefly through the bronchial, but partly through the pulmonary, veins. 

 Lymphatics. The lymphatics are arranged in three sets: i. Ir- 

 regular lacunae in the walls of the alveoli or air-cells. The lymphatic vessels 

 which lead from these accompany the pulmonary vessels toward the root 

 of the lung. 2, Irregular anastomosing spaces in the walls of the bronchi. 

 3, Lymph spaces in the pulmonary pleura. The lymphatic vessels from all 



