502 THE THORAX AND VERTEBRAL COLUMN 



THE THORAX AND VERTEBRAL COLUMN. 



THE THORACIC WALL. 



Surface Landmarks. The upper border of the manubrium 

 sterni, which is on the same horizontal level as the fibre-cartilage 

 between the second and third thoracic vertebrae, can be felt 

 in the jugular (supra-sternal) notch. 



The junction between the manubrium and the body of the 

 sternum is marked by a transverse ridge, which is known as the 

 sternal angle (of Louis). The second costal cartilage articulates 

 with the sternum at the lateral extremity of the sternal angle 

 and can always be identified with certainty. As the first costal 

 cartilage is obscured by the clavicle, the sternal angle is a 

 valuable landmark when it is necessary to identify the individual 

 ribs. 



The anterior halves of the second and third ribs are almost 

 horizontal, and the corresponding interspaces are widest near 

 the sternum. The lower costal cartilages ascend with increasing 

 degrees of obliquity, and the corresponding interspaces are 

 greatest at the junction of the ribs with their cartilages. 



The muscular landmarks produced by the pectoralis major 

 (p. 2) and the muscles of the back (p. 239) have already been 

 described. 



The apex-beat of the heart is felt in the fifth intercostal space, 

 3^ inches from the median plane. It is not always visible, 

 but it can always be felt, especially if it is accelerated and 

 strengthened by slight physical exercise. 



Fracture of the Ribs may result either from direct or 

 from indirect violence. In the former case, the broken ends are 

 forced inwards. They may penetrate the pleura and wound 

 the lung, or they may pierce the diaphragm and injure the liver 

 or the spleen. Hsemo-thorax, pneumo-thorax, or surgical 

 emphysema may result. 



When the injury is due to indirect violence, the thorax being 

 compressed antero-posteriorly, the rib commonly breaks just 

 in front of its angle, and the fragments, which subsequently 

 tend to overlap, are in the first place forced outwards. On 



