22 SUPERFICIAL ANATOMY OF THE TRUNK. 



line, and generally about an inch and a half (4 cm.) below, and three-quarters of an 

 inch (2 cm.) to the sternal side of the nipple. The right border of the heart is indicated 

 by a line carried from the third to the seventh chondro-sternal articulation, and 

 arching outwards to a distance of one inch and a half (4 cm.) from the middle line ; 

 the left border, by an oblique line, convex upwards, extending from the second left 

 costal cartilage to the apex. The area thus marked out corresponds to what is known 

 as the deep cardiac dulness, although the latter can hardly be traced above the third 

 costal cartilage of the left side ; the superficial cardiac dulness corresponds to that 

 part of the heart which is uncovered by lung, and thus begins at the inner end of the 

 fourth left cartilage, extends to the left almost to the apex, to the right as far as the 

 middle line, and below merges into the dulness which answers to the liver. 



The pulmonary orifice is placed opposite the upper margin of the third left costal 

 cartilage, close to the sternum, whence the artery proceeds upwards to its bifurcation 

 behind the second costal cartilage of the same side, which is therefore termed the 

 pulmonary cartilage. The orifice of the aorta is below and a little internal to the 

 pulmonary orifice, being behind the sternum, close to the lower border of the third 

 left cartilage ; from this spot the ascending aorta passes across to the right edge of 

 the sternum opposite the second (aortic} cartilage, and the arch then returns to the 

 left side, crossing the middle line about an inch (2'5 cm.) from the suprasternal 

 depression. Opposite the middle point of the manubrium, the innominate and left 

 common carotid arteries are arising close together from the upper border of the arch 

 of the aorta, and they pass symmetrically upwards, the innominate to the back of the 

 right, and the carotid to the back of the left sterno-clavicular articulation. The left 

 subclavian artery is almost directly behind the left carotid in the thorax. The superior 

 vena cava lies to the right of the arch, behind the inner ends of the first and second 

 intercostal spaces ; and the left innominate vein, resting on the upper border of the 

 arch, is just below the upper margin of the sternum. It sometimes happens, how- 

 ever, especially in children, that the arch of the aorta is placed at a higher level 

 than usual, and then the left innominate vein projects upwards into the neck. In 

 other cases the innominate artery is longer than usual, and may be felt pulsating in 

 the suprasternal fossa. 



The auriculo-ventricular openings of the heart are lower down than the arterial 

 orifices, the left being behind the inner end of the fourth left costal cartilage and 

 the adjoining part of the sternum, while the right lies behind the sternum on a 

 level with the fourth interspace and fifth cartilage. 



Arteries of the thoracic wall. The internal mammary artery descends behind 

 the costal cartilages, and across the inner ends of the upper six intercostal spaces, 

 about half an inch (1 cm.) from the margin of the sternum ; and it occasionally gives 

 off a considerable lateral costal branch which runs downwards on the inner surface of 

 the ribs along the side of the thorax (Vol. II, p. 429). The intercostal vessels are 

 lodged for the greater part of their extent in the grooves beneath the lower edges of 

 the ribs, by which they are thus protected. 



THE ABDOMEN. 



The superficial limits of the abdomen are formed above by the lower margin or 

 the thorax, and below by Poupart's ligament and the iliac crest on each side, the 

 former corresponding, except in fat persons, to the curved inguinal furrow. The 

 abdominal cavity, however, extends considerably beyond these limits, both upwards 

 into the vault of the diaphragm, under cover of the lower ribs and their cartilages, 

 and downwards into the hollow of the pelvis. The abdomen is arbitrarily divided 

 into nine regions by two horizontal and as many vertical lines. Of the horizontal 

 lines, one, called infracostal, is drawn across at the level of the lowest point of the 

 tenth costal arch on each side, and the other, which may be termed bi-iliac, between 



