210 MICROSCOPIC ANATOMY OF THE ORGANS. 



or more terminal bronchi, which are the same as the alveolar 

 ducts. The alveolar sacs or infundibula correspond with Miller's 

 air sacs. The term alveolus is applied to the air cells (Schulze, 

 Kolliker). 



The interlobular connective tissue contains many elastic 

 fibres, and often a considerable amount of pigment, such as 

 coal-dust breathed into the lungs. These foreign particles are 

 carried away by the lymphatics to the lymph glands at the 

 base of the bronchi, where usually they are retained. 



The pleurae consist of connective tissue containing a good 

 deal of elastic tissue, and are covered on their free surface by 

 flat endothelial cells. 



The pulmonary artery, carrying venous blood to the lungs, 

 breaks up into many branches, which accompany the bronchi. 



FIG. 162. 



Part of a section of an injected lung from a rabbit. 3()0. The alveoli are seen from the 



surface ; at a an alveolus is cut through. 



The arterial end twigs form a capillary network which sur- 

 rounds the alveoli (Fig. 162). One terminal twig usually 

 supplies several alveoli. From this capillary network venous 

 branches proceed to the bases of the bronchi and carry out the 

 arterial blood to the pulmonary rein. During its passage 

 through the capillary network surrounding the alveoli the 

 venous blood absorbs the oxygen of the air through the walls 



