CH. XXVI.] BLOOD-SUPPLY OF THE LUNGS 353 



interchange of gases, in a compact organ. The total surface of the 

 inside of the lung has been variously calculated, but it may be taken 

 to be about 90 square metres in the adult, or about the size of a 

 carpet necessary to cover the floor of a good-sized room (10 yards 

 by 12). 



The vesicles of adjacent lobules do not communicate; so that, 

 when any bronchial tube is closed or obstructed, the supply of air is 

 lost for all the sacs opening into it or its branches. 



Blood-supply. The lungs receive blood from two sources, (a) the 

 pulmonary artery, (b) the bronchial arteries. The former conveys 

 venous blood to the lungs to be arterialised. The branches of the 

 bronchial arteries convey arterial blood from the aorta for the 



FIG. 289. Capillary network of the pulmonary blood-vessels in the human lung. 

 X 60. (Kolliker.) 



nutrition of the walls of the bronchi, of the larger pulmonary vessels, 

 of the interlobular connective tissue, etc. ; the blood of the bronchial 

 vessels is returned chiefly through the bronchial and partly through 

 the pulmonary veins. 



Lymphatics. The lymphatics consist of irregular lacunre in the 

 walls of the air-sacs, in the walls of the bronchial tubes, and in the 

 pulmonary pleura. The lymphatic vessels from all these irregular 

 sinuses pass in towards the root of the lung to reach the bronchial 

 lymphatic glands. 



Nerves. The nerves of the lung contained in the anterior and 

 posterior pulmonary plexuses are formed by branches of the vagus 

 and sympathetic. They follow the course of the vessels and bronchi, 

 and in the walls of the latter many small ganglia are situated. 



