STRUCTURE OF LUNG. 



487 



marked with black. The surface is figured with irregularly polygo- 

 nal outlines which represent the lobules of the organ, and the area 

 of each of these polygonal spaces is crossed by lighter lines. 



Fig. 147 * 



Each lung is divided into two lobes, by a long and deep fissure 

 which extends from the posterior surface of the upper part of the 

 organ, downwards and forwards to near the anterior angle of its 

 base. 



In the right lung the upper lobe is subdivided by a second fissure, 

 which extends obliquely forwards from the middle of the preceding 

 to the anterior border of the organ, and marks off a small triangular 

 lobe. 



The Right lung is larger than the left, in consequence of the in- 

 clination of the heart to the left side. It is also shorter, from the 

 great convexity of the liver, which presses the diaphragm upwards 

 upon the right side of the chest considerably above the level of the 

 left. It has three lobes. 



The left lung is smaller, has but two lobes, but is longer than the 

 right. 



* Anatomy of the heart and lungs. 1. The right ventricle ; the vessels to the right 

 of the figure are the middle coronary artery and veins ; and those to its left, the ante- 

 rior coronary artery and veins. 2. The left ventricle. 3. The right auricle. 4. The 

 left auricle. 5. The pulmonary artery. 6, 6. The right pulmonary artery. 7. The 

 left pulmonary artery. 8. The remains of the ductus arteriosus. 9. The arch of the 

 aorta. 10. The superior vena cava. 11. The right vena innominata, and the arteria 

 innominata. 12. The right subclavian artery and vein. 13. The right common 

 carotid artery and vein. 14. The left vena innominata. 15. The left carotid artery 

 and vein. 16. The left subclavian artery and vein. 17. The trachea. 18. The right 

 bronchus. 19. The left bronchus. 20, 20. The pulmonary veins; 18, 6, 20, form the 

 root of the right lung; and 7, 19, 20, the root of the left. 21. The superior lobe of 

 the right lung. 22. Its middle lobe. 23. Its inferior lobe. 24. The superior lobe of 

 the left lung. 25. Its inferior lobe. 



