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1186 SURFACE AND SURGICAL ANATOMY. 
dorsal vertebrae. Jimmediately below the xiphi-sternal articulation is the imfra- 
sternal notch, formed by the junction of the seventh costal cartilages with the 
sternum. Below the notch is the epigastric fossa or triangle, bounded laterally by 
the seventh costal cartilages. The apex of the triangle forms an angle which 
varies considerably according to the shape of the chest, the average being about 
f0= Not infrequently the eighth costal cartilage articulates with the sternum. 
Fracture of the sternum is rare, and generally occurs at or close to the junction of the manu- 
briuimn and the body ; it may occur either from direct violence, or indirectly along with fracture 
of the spine. Unlike that of the ribs, the periosteum covering the sternum is firmly adherent 
to the bone. * 
The ribs, which in well-nourished subjects cause no surface prominences, are 
readily visible in thin persons; in the obese they are very difficult to feel. In 
counting the ribs from the front, the second may always be identified by its relation 
to the angulus Ludovici. The first rib is toa large extent under cover of the clavicle. 
The lower border of the pectoralis major and the first visible digitation of the 
serratus magnus afford reliable guides to the fifth rib. The infra-sternal notch is 
the guide to the inner end of the seventh costal cartilage. The second and third 
costal cartilages are practically horizontal; below this the cartilages ascend with 
increasing obliquity, that of the sixth being the first to present a distinct angle. 
The inner end of the second intercostal space is the widest, while those of the fifth 
and sixth are very narrow. 
The costo-chondral junctions may be indicated on the surface by a line drawn 
from the upper end of the para-sternal line to a point a finger’s breadth behind the 
angle of the tenth costal cartilage. 
The internal mammary artery crosses behind the inner ends of the upper five 
intercostal spaces about 4 in. from the edge of the sternum; as it descends it 
approaches a little nearer to the sternum. The vessel is accompanied by two 
veins which unite to form a single vein opposite the second interspace. 
This artery is occasionally injured in punctured wounds of the chest. At the second or third 
intercostal space it is easily ligatured through a transverse incision, but at a lower level it is 
generally necessary to resect a ‘portion of one of the costal cartilages. 
THE LUNGS. 
The apex of the lung extends upwards into the root of the neck for a distance 
of 1 to 2 in. above the anterior extremity of the first rib, and 1s mapped out by 
a curved line drawn from the upper border of the sterno-clavicular articulation 
across the sterno-mastoid to the junction of the inner and middle thirds of the 
clavicle, the highest part of the curve reaching from 4 to 14 in. above the clavicle. 
The apex of the right lung reaches 4 in. higher than that of the left lung. Inti- 
mately related to the apex of the cervical pleura are the subclavian artery and 
the inferior cervical ganglion of the sympathetic. 
Both the cervical pleura and the subclavian artery may be injured by one of the fragments in 
a fracture of the clavicle ; the scaleni muscles, however, affording considerable protection to the 
former. In hgaturing the third part of the stbelavian artery, care must be taken not to mjure 
the cervical pleura. 
To delineate the anterior border of the right lung, draw a line from the upper 
border of the sterno-clavicular articulation to the centre of the manubrium 
sterni, and from thence vertically downwards, in or slightly to the left of the 
middle line, to the level of the sixth or sev enth costal cartilage, or it may be even 
to the infra-sternal notch. 
The anterior border of the left lung is mapped out by a corresponding line as 
far as the fourth costal cartilage; thence it is directed outwards along the lower 
border of the fourth costal cartilage to the para-sternal line; it then passes down- 
wards and slightly outwards across the fourth interspace, and curves inwards 
behind the fifth costal cartilage and fifth interspace to reach the upper border of 
the sixth costal cartilage in the para-sternal line. The lower part, therefore, of the 
anterior surface of the right ventricle is uncovered by lung and gives a completely 
