134 ANATOMY FOR, NURSES [CHAP. XII. 



Broadly speaking, the lungs may be said to consist of a large 

 amount of a film-like elastic membrane, covered by a close net- 

 work of blood-vessels, which membrane is arranged in the form 

 of irregularly dilated pouches at the end of fine tubes, opening 

 into larger and larger tubes, and finally into the windpipe, 

 which places them in communication with the external air. 



By virtue of their structure, the larger bronchial tubes 

 remain permanently open ; the smaller tubes, however, are sub- 



FIG. 92. ANTERIOR VIEW OF LUNGS AND HEART. 1, heart; 2, inferior vena 

 cava ; 3, superior vena cava ; 4, right innominate vein ; 5, left innominate vein ; 

 6, jugular vein; 7, subclavian vein; 8, arch of aorta; 8', subclavian artery; 9, left 

 pulmonary artery; 9', 9', carotid artery; 10, trachea; 11, left bronchus; 12, rami- 

 fications of right bronchus exposed in upper lobe of right lung ; 13, 14, middle lobe ; 

 15, lower lobe; It), upper lobe of left lung; 17, lower lobe of left lung. 



ject to collapse when empty; they also may contract under 

 certain nervous influences. The terminal dilatations are emi- 

 nently elastic and continually expand and contract; they are 

 bathed with lymph, and are always moist. 



The two lungs occupy almost all the cavity of the thorax 

 which is not taken up by the heart. The right lung is the 

 larger and heavier; it is broader than the left, owing to the 

 inclination of the heart to the left side ; it is also shorter by one 



