THE BRONCHI. 



147 



artery, on the other. The size of the pulmonary vessels 

 always corresponds to that of the accompanying bronchus, 

 being not far from equal to it. 



The bronchial vessels are much smaller than the pulmonary, 

 and serve for the nutrition of the substance of the lung. 

 The bronchial arteries are branches of the aorta. The capil- 

 laries from these arteries empty chiefly into the bronchial 

 veins, but partly also into the pulmonary veins. The bron- 

 chial veins empty ultimately into the vena cava. 



The bronchial vessels lie in the peribronchial connective 

 tissue and accompany the bronchi and pulmonary vessels in 

 their ramifications. 



The lymphatics of the lungs comprise small channels origin- 



FIG. 61. 



Portion of bronchiole (pig) in cross-section (Schultze). a, submucosa; b, mus- 

 cularis mucosae ; c, tunica propria ; d, epithelium ; /, portions of neighboring 

 air-vesicles. 



atingfrom stomata in the air- vesicles, in the sustentacular and 

 perivascular tissue, and from the pleural stomata. 



The nerves of the lungs are small branches lying in the 

 peribronchial tissue. 



The bronchi are continuations of the trachea, and within 

 the lung divide and subdivide dichotomously down to the 

 terminal bronchioles (Fig. 61). They are the air-passages to 



