1368 CLINICAL AND TOPOGRAPHICAL ANATOMY 



the angle of the scapula (the arms being close to the sides), the tenth rib. The 

 position of the great fissure in each lung may be ascertained approximately by 

 drawing a line curving dowTiward and forward from the second thoracic spine 

 to the lower border of the lung at the sixth costal cartilage; and the smaller fissure 

 of the right lung extends from the middle of the foregoing to the junction of the 

 fourth costal cartilage with the sternum. It will be seen from the above that 

 there is little lung behind the manubrium. The connective tissue here between 

 the lung margins contains the thymus, large up to the age of puberty, and, later, 

 its remains. The hilus (root) of the lung is referred to on p. 1230. 



The pleura, follo^\ang much the same line as the lung above and in front, 

 reaches lower down laterally and behind. Thus the two sacs starting from about 

 2.5 cm. (1 in.) above the medial third of the clavicle converge toward the angle 

 of Louis (p. 1238) ; meeting here, they descend vertically, the left overlapping the 

 right slightly, to the fourth chondro-sternal joint. Hence the right sac descends 

 behind the sternum to the sterno-xiphoid junction and sixth chondro-sternal 

 joint. Thence, as it curves to the back of the chest, it crosses the eighth rib 

 close to the lateral vertical line (vide supra), the tenth in the mid-axillary, the 

 eleventh in the line of the angle of the scapula, and thence toward the twelfth 

 thoracic vertebra. On the left side the pleura parts company from the right at the 

 level of the fourth chondro-sternal junction, deviating laterally and downward 

 across the fourth and fifth interspaces; it then turns again slightly medially to 

 meet the sixth costal cartilage. Thus, as in the case of the lung, but to a less 

 extent, there is a small area of the pericardium, and, under it, the right ventricle 

 uncovered by the pleura. Over the side and back of the chest, along its dia- 

 phragmatic reflection, the left pleura reaches a Httle lower than the right. 



The deepest part of the pleural sac is where the reflection crosses the tenth rib or tenth space 

 in the mid-axillary line. From this it ascends slightly as it curves back to the spine. (Cun- 

 ningham.) The relations of the pleura to the last rib are of much importance to the surgeon in 

 operations on the kidney. In the case of a twelth rib of ordinarj^ length, the pleural reflection 

 crosses it at the lateral border of the sacro-spinalis; when a rudimentary last rib does not reach 

 the lateral border of this muscle, an incision carried upward into the angle between the eleventh 

 rib and the sacro-spinalis will open the pleural sac. (Melsome.) 



For tapping the pleura there are two chief sites: — (1) The sixth or seventh space in front 

 of the posterior fold of the axilla. (2) The eighth space behind, in the line of the angle of the 

 scapula. For the incision of an empyema the first is usually chosen. The overlying soft parts 

 are not thick, the interspace is wide enough, drainage is sufficient (especially if part of the 

 seventh or eighth rib be re.sected), and this site is free from the objection that the angle of the 

 scapula overlaps the seventh and eighth ribs, unless the arm is raised. 



Outline of the heart. Its relation to the chest-wall. — The upper limit of 

 the heart (base) will be defined by a line crossing the sternum a little above the 

 upper border oif the third costal cartilage, reaching about 1.2 cm. (| in.) to the 

 right and about 2.5 cm. (1 in.) to the left of the sternum. Its apex point is in the 

 fifth space, 3.7 cm. (1^ in.) below the male left nipple, and 2.5 cm. (1 in.) to the 

 medial side. This point will be at 7.5 cm. (3 in.) from the left border of the 

 sternum. The right border (right atrium) will be given by a line, slightly convex 

 laterally, drawn from the right extremity of the upper border to the right sixth 

 chondro-sternal joint. If another line, slightly convex upward, be drawn 

 onward from this point across the last piece of the sternum, just above the 

 xiphoid cartilage, to the apex, it will give the lower border (margo acutus of right 

 ventricle), which rests on the central tendon of the diaphragm. The left border 

 (margo obtusus of left ventricle) will be given by a line, convex to the left, passing 

 from the left extremity of the upper ])order to the apex, medial to the nipple- 

 line. This line should be 7.5 cm. (3 in.) from the middle of the sternum at the 

 level of the fourth costal cartilage. The l)asc of the heart is opposite four of 

 the thoracic vertebra3, viz., the sixth, seventh, eighth, and ninth. The apex 

 and anterior or costo-sternal surface have been mentioned. The inferior or 

 diaphragmatic surface (chiefly left atrium and left ventricle) rests upon the 

 diaphragm, mainly the central tendon, to which the intervening pericardium 

 is connected, and is thus adjacent to the liver and a small portion of the stomach. 



If a circle 5 cm. (2 in.) in diameter be described around a point midway between the left 

 nipple and the lower end of (ho gladiolus, it will dcliiH" with sudicient accuracy for practical 

 purposes that part of the heart which lies inuiiediatoly behind the chest wall, and which is 

 uncovered by lung and (in part) by pleura. (Latham.) 



