THE BRONCHI 411 



at this point. The relations of the structures within the root 

 are: From above downward, on the right side, the bronchus, 

 the pulmonary artery, pulmonary veins; the left side, pulmonary 

 artery, bronchus, pulmonary veins. On the right side only the 

 eparterial branch of the bronchus lies above the pulmonary 

 artery. 



The true weight of the human lungs as ascertained in the 

 bodies of criminals executed by electricity, in which the mode 

 of death is attended by a nearly bloodless condition of the 

 lungs, is 215 grams (7^ ounces) for the left lung and 240 grams 

 (8J ounces) for the right lung (E. A. Spitzka, Amer. Jour, 

 of Anal., iii, i, p. v). Ordinarily, with the vascular channels 

 more or less filled with blood and serum, the two lungs to- 

 gether weigh about 42 ounces, the right lung being 2 ounces 

 heavier than the left, but much variation is met with according 

 to the amount of blood or serous fluid they may contain. The 

 lungs are heavier in the male than in the female. The specific 

 gravity of the lung tissue varies from 0.345 to 0.746. (Gray.) 



The color of the lungs at birth is a pinkish white; in adult 

 life, a dark slate color, mottled in patches; and as age advances 

 this assumes a black color. (Gray.) 



The lungs are composed of an external serous coat, sub- 

 serous areolar tissue, and parenchyma, consisting of the lobules 

 Q inch to li inches in size), the terminal bronchioles ending 

 in the alvei, air sacs, or infundibula and the alveoli or saccules; 

 the ramifications of the bronchial and pulmonary arteries, 

 lymphatics and nerves. These are connected by fibroelastic 

 tissue. The blood supply of the lungs is received from the 

 bronchial artery, a branch of the thoracic aorta, and the pul- 

 monary arteries, which are the nutrient vessels of the respiratory 

 epithelium. The bronchial arteries supply the bronchi, bron- 

 chioles, and interlobular tissues, as well as the walls of the 

 pulmonary vessels. The right bronchial veins empty into the 

 vena azygos major, the left bronchial veins empty into the left 

 superior intercostal vein or the vena hemiazygos accessoria vein. 



THE BRONCHI 



The Right. Enters the hilum of the lung. About one inch 

 from the trachea it gives off a branch above the pulmonary 



