1188 SURFACE AND SURGICAL ANATOMY. 
dull note on percussion ; this area is spoken of as the area of “ superficial or absolute 
cardiac dulness.” 
The level of the lower border of the lung is practically the same on both sides; 
it is mapped out by a line extending outwards from the lower extremity of the 
anterior border and passing through the sixth costal cartilage im the mid-clavicular 
line, and thence in a slightly curved direction, with the convexity downwards, 
across the lateral aspect of the chest to the tenth dorsal spine. This line crosses 
the eighth rib in the mid-axillary line and the tenth rib in the scapular line. 
To indicate the position of the oblique fissures a line is drawn from the 
second dorsal spine across the interscapular region to the root of the spine of the 
scapula, and thence downwards and outwards across the infraspinous fossa, to end 
at the lower border of the lung opposite the sixth costal cartilage, a finger’s 
breadth external to the para-sternal line. When the arm is raised above the level 
of the shoulder, and the hand placed on the back of the head, the inferior angle of 
the scapula is rotated upwards and forwards so that the vertebral border practi- 
cally corresponds with the line of the oblique fissure. 
The transverse fissure of the right lung is mapped out by drawing a line from 
the anterior border of the lung, at the level of the fourth costal cartilage, outwards 
and slightly upwards to join the middle of the oblique fissure. 
Pleura.—The line of reflexion of the right pleura from the back of the sternum 
may be said to correspond to the anterior border of the right lung. 
On the left side, the pleural reflexion corresponds to the anterior border of the 
left lung as far as the lower edge of the fourth chondro-sternal junction, from 
which point it diverges slightly and descends behind the left border of the sternum 
to the sixth costal cartilage. 
The right costo-diaphragmatic reflexion (see Figs. 802 and 805) is mdicated on 
the surface by a line drawn from the seventh chondro-sternal junction (sometimes 
the infra-sternal notch) downwards and outwards to a point 2 in. vertically above 
the angle of the tenth costal cartilage; from this pot the line is carried with a 
slightly downward curve across the lateral aspect of the chest to the twelfth 
rib at the outer margin of the erector spine; thence it passes below the twelfth 
rib and reaches the vertebral column at the level of the upper border of the 
twelfth dorsal spine. 
The left costo-diaphragmatic reflexion is indicated by a line drawn from a point 
opposite the sixth costal cartilage, a finger’s breadth from its Junction with the 
sternum, to a point one and a half inches vertically above the angle of the tenth 
costal cartilage, and thence to the spine, as on the right side, but at a shghtly lower 
level. 
The costo-diaphragmatic reflexion reaches its lowest limit in the mid-axillary 
line two inches vertically above the tip of the eleventh costal cartilage, a level 
which may be readily indicated, according to Cunningham, by a point in the mid- 
axillary line intersected by a horizontal line drawn round the trunk at the level of 
the lowest part of the extremity of the first lumbar spine. The same author 
localises the level of the diaphragmatic pleural reflexion in the mammary lne at 
the point where this line is intersected by another horizontal line at the level of 
the spine of the last dorsal vertebra. 
The relations of the pleura to the twelfth rib are of importance to the surgeon, 
especially in connexion with operations on the kidney (Fig. 631, p. 931). When this rib is 
not abnormally short, the pleural reflexion crosses it opposite the outer border of the 
erector spinee muscle, hence an incision may be carried deeply as far as the apex of the 
angle formed by the twelfth rib and the outer border of the erector spine without entering 
the pleura. When, however, the twelfth rib does not reach the outer border of the erector 
spine, an incision carried upwards into the apex of the angle between this muscle and the 
eleventh rib is certain to wound the pleura (Melsome). It is important, therefore, to 
count the ribs from above downwards, in order not to mistake the eleventh for the twelfth, 
when the latter is rudimentary. 
Internal to the outer edge of the erector spinze the pleural reflexion lies below the 
level of the twelfth rib, and not infrequently descends as far as the transverse process 
of the first himbar vertebra. 
