316 



THE RESPIRATORY SYSTEM 



ceedingly dense net of anastomosing vessels in the walls of the alveoli, 

 the meshes of the capillary net being frequently, in the deeper portions 

 of the lung, of less diameter than the vessel itself. At the periphery of 

 the lobule the capillaries converge to form several venules which unite 

 to form larger veins in the interlobular tissue. These veins pursue an 



FIG. 299. FROM THE LUNG OF A DOG WHOSE BLOOD-VESSELS HAD BEEN INJECTED 

 WITH A GELATINOUS MASS, AND APPEAR BLACK. 



The outlines of the pulmonary alveoli and atria are well shown. Many of the 

 alveoli have been cut tangentially and present a surface view of the capillary net- 

 work; in others the alveolar wall is out across and is seen in profile. X 125. 



independent course and are always found at a considerable distance from 

 the bronchioles and lobular branches of the pulmonary artery. (See 

 Fig. 290.) 



The smaller branches of the pulmonary artery near the surface of 

 the lung give arterial twigs to the adjacent portions of the pleura. 

 From the capillaries of the pleura minute venules enter the interlobular 

 tissue and join the interlobular veins. 



