Chap. x.i THE THORAX. 155 



thoracic artery, and the external mammary. The 

 majority of the lymphatics from the breast proceed to 

 the axilla. Some few follow the mammary branches 

 of the internal mammary artery, and enter the 

 anterior mediastinal glands, which are consequently 

 often found enlarged in cancer of the organ. 



As the chief blood- supply of the breast comes 

 from the axilla, and as the main lymph vessels pro- 

 ceed to that region, it follows that malignant growths 

 of the gland tend to spread towards the axilla rather 

 than towards the middle line. 



2. The thoracic viscera. 



The lung*. The apex of the lung rises in the neck 

 from one to one arid a half inches above the clavicle. 

 The anterior edges of the two lungs lie behind the 

 sterno-clavicular articulations, pass obliquely behind 

 the manubrium, and meet in the middle line at the 

 junction of the manubrium with the gladiolus. The 

 edge of the right lung then continues vertically down- 

 wards behind the middle line of the sternum to the 

 sixth chondro-sternal articulation, where it slopes off 

 along the line of the sixth rib. The edge of the left 

 lung keeps close to that of the right as far as the fourth 

 chondro-sternal articulation, where it turns off to the 

 left, following a line drawn from the fourth cartilage 

 to the apex of the heart. The lower border of the 

 lung corresponds to a slightly convex line drawn round 

 the chest from the sixth chondro-sternal articulation 

 in front to the tenth dorsal spine behind. In the 

 mammary line this line would correspond to the sixth 

 rib, opposite the posterior fold of the axilla with the 

 eighth rib, and in a line continued vertically down- 

 wards from the inferior angle of the scapula with the 

 tenth rib. The pleura extends further down than 

 the lung, reaching in front to the level of the seventh 

 chondro-sternal union, behind to the eleventh dorsal 

 spine, and at the sides to a point some two and a half 



