THE LUNGS. 



197 



have the flat chest. Enlargement of the chest posteriorly is impossible on account.of 

 the support of the ribs, vertebrae, and strong back muscles. Enlargement downward 

 is allowed by a descent of the diaphragm ; hence the fulness of the abdomen in those 

 affected with emphysema and conversely the flatness of the abdomen in tMose having 

 phthisis. In the region of the apices the thorax is closed by the deep fascia, which 

 spreads from the trachea, oesophagus, muscles, and great vessels and blends with the 

 pleura to be attached to the first rib. In the normal condition this is level with the 

 plane of the first rib and rises little if at all above it. Even in disease it is not 

 materially altered. This is certainly so in phthisis and probably so in emphysema. 

 The apparent fulness of the supraclavicular fossae and intercostal spaces in emphysema 

 and the increased depth of these hollows in phthisis are not due so much to a bulging 

 or to a retraction of the lungs at these points as to the atrophy of the fatty and 

 muscular tissue in phthisis and to the muscular tension in emphysema. 



In coughing, the apex of the lung does not jump up into the neck above the 

 clavicle as it appears to do, but remains nearly or quite below the plane of the top of 

 the first rib. The appearance of bulging is caused by the movements of the trachea 

 in the median line and the muscles laterally. This is noticeable particularly in the 



Sternothyroid muscle 



Carotid artery 



Sternohyoid muscle 



Subclavian artery 

 Vagus nerve 



Carotid artery 



Vagus nerve 



First rib - 



Scalenus anticus 



muscle 



Subclavian vein 



Subclavian artery 



Pleura 



Subclavian vein 



- First rib 



Pleura 



Trachea 



(Esophagus 



FIG. 216. Upper end of the thorax, at the level of the first rib. 



case of the platysma and omohyoid muscles. In quiet breathing the posterior belly 

 of the omohyoid lies about level with the clavicle, but in coughing it rises i or 2 cm. 

 above it. The intercostal membranes and muscles are kept tense by the constant 

 elevation of the ribs due to the muscular tension. 



OUTLINE OF THE LUNGS. 



Apex. The apex of the lung has its highest point opposite the posterior 

 extremity of the first rib. It then follows the plane of the top of the first rib down 

 to the sternoclavicular joint, immediately above the junction of the cartilage of the 

 first rib with the sternum. The anterior end of the first rib is 5 cm. lower than the 

 posterior. The upper edge of the clavicle is 2. 5 cm. or one inch, above the anterior 

 end of the first rib and 2.5 cm. below the head of the first rib, hence the apex of the 

 lung rises 2.5 cm. (i in.) above the clavicle, and it lies behind its inner fourth. 

 This distance will vary in different individuals with the obliquity of the ribs. The 

 more oblique the ribs the greater will be the distance between the level of the top of 

 the clavicle and that of the neck of the first rib. 



Anterior Border. From the sternoclavicular joint the borders of the lungs 

 pass downward and inward until they almost or quite touch in the median line at the 

 angle of Ludwig opposite the second costal cartilage. They continue downward 



