THE CHEST. 21 



muscles. It is important as a guide to the coracoid process 

 and the axillary artery. In a case of injury to the shoulder, 

 to ascertain whether the coracoid process is broken, carry the 

 arm outwards, to put the deltoid and pectoral muscles on the 

 stretch, and make manifest the space between their opposite 

 borders. Pressing the thumb into the space we can feel 

 the inner side of the coracoid process, the apex being under 

 the fibres of the deltoid ; thus it is easy to ascertain whether 

 it be broken. Moreover, this space corresponds with the line 

 of the axillary artery ; here its pulsation can be distinctly 

 felt, and here it can be compressed (but not easily, or for 

 long) against the second rib. 



40. Internal mammary artery. The line of the internal 

 mammary artery runs perpendicularly behind the cartilages 

 of the ribs, about half an inch from the sternum. The per- 

 forating branch through the second intercostal space is gene- 

 rally the largest. 



41. Outline of heart on chest- wall. To have a general 

 idea of the form and position of the heart, map its outline on 

 the wall of the chest, as follows : 



a. To define the base draw a transverse line across the 

 sternum corresponding with the upper borders of the third 

 costal cartilages : continue the line half an inch to the right 

 of the sternum and one inch to the left. 



b. To find the apex, mark a point about two inches below 

 the left nipple, and one inch to its sternal side. This point 

 will be between the fifth and sixth ribs. 



c. To find the lower border (which lies on the central 

 tendon of the diaphragm), draw a line, slightly curved down- 

 wards, from the apex across the bottom of the sternum (not 

 the ensiform cartilage) as far as its right edge. 



d. To define the right border (formed by the right auricle), 

 continue the last line upwards with an outward curve, so as to 

 join the right end of the base. 



e. To define the left border (formed by the left ventricle), 

 draw a line curving to the left, but not including the nipple, 

 from the left end of the base to the apex. 



Such an outline (seen in the cut, page 22, with the angles 



