1190 SURFACE AND SURGICAL ANATOMY. 
mediastinum, there is less risk of opening the pleura if the space be entered from the left 
side of the vertebral column. 
The seat of election for tapping the pleura (paracentesis pleure) is the sixth or seventh 
costal interspace a little in front of the posterior axillary fold. To allow of the introdue- 
tion of a tube to drain away the pus from the pleural cavity im empyema, a portion ef one 
of the ribs (sixth to ninth) is resected. The intercostal vessels and nerves, which lie in the 
eroove at the lower border of the rib, are avoided by removing the portion of bone sub- 
periosteally. . If the chest is opened in the scapular line care must be taken not to resect 
either the seventh or the eighth ribs, which are exposed when the arm is elevated, but 
overlapped by the angle of the scapula when the arm is lowered. 
Anteriorly, the bifurcation of the trachea les at or a little below the angulus 
Ludovict, while posteriorly it les a little below the level of the root of the spine 
of the scapula, opposite the interval between the third and fourth dorsal spines. 
The bifureation takes place one vertebra higher in the infant than in the adult 
(Symington). 
The right bronchus is wider and more nearly in a line with the trachea than 
the left bronchus, hence the greater tendency of foreign bodies to enter the 
former. 
The roots of the lungs are situated opposite the fourth, fifth, and sixth dorsal 
spines, midway between them and the vertebral borders of the scapulee. 
The lower end of the trachea, the bronchi, the vagi, and the left recurrent laryngeal nerve, 
are all more or less surrounded by lymphatic glands, which, when enlarged, may exert injurious 
pressure upon them. 
THE HEART AND GREAT VESSELS. 
Viewed from the front, the outline of the precordial area, like that of the peri- 
cardial sac, is roughly triangular, the base of the triangle being below and the apex 
above. The boundaries are delineated upon the surface as follows :— 
The right side of the triangle, formed by the right auricle, is indicated by 
drawing a lne slightly convex outwards from the upper end of the third to the 
sixth (frequently the seventh) right chondro-sternal junctions ; the curve attains its 
maximum opposite the fourth intercostal space, where it reaches 13 in. from the 
middle line. 
The base of the triangle, formed by the margo acutus of the right ventricle and 
to a very slight extent by the apical portion of the left ventricle, is almost 
horizontal, and corresponds to a line drawn from the sixth or seventh right 
chondro-sternal junction to the apex of the left ventricle, which lies behind the 
fifth left intercostal space, 35 in. from the middle line and } in. internal to the 
mid-clavieular line. The hase line crosses the xiphoid cartilage a little below its 
junction with the body of the sternum. 
The left side of the triangle, formed by the margo obtusus of the left ventricle, is 
indicated by a slightly curved line extending from the apex of the heart upwards 
and inwards to the lower edge of the second ‘left chondro-sternal articulation, the 
convexity of the curve being directed outwards and slightly upwards. 
The truncated apex of the triangle, which lies behind the sternum at the level 
of the second intercostal space, corresponds to the highest part of the heart, 
namely, where the auricular appendices embrace the aorta and pulmonary artery. 
The anterior part of the right auriculo-ventricular groove is mapped out by a 
line drawn from the middle line, opposite the lower border of the third right costal 
cartilage, downwards and outwards to the sixth right chondro-sternal junction ; 
the line should be shehtly convex upwards and to the right. The right auricular 
appendix lies at, or a little to the left of, the middle line, at the level of the second 
intercostal space and the upper border of the third costal cartilage. The left 
auricular appendix lies behind the second left intercostal space, close to the edge of 
the sternum. 
The inferior surface of the heart (facies diaphragmatica) rests upon the dia- 
phragmatic or basal part of the pericardium. The true posterior surface of the 
heart is formed mainly by the left auricle, which is moulded posteriorly upon the 
cesophagus, the left bronchus and the bronchial glands, the pericardium intervening. 
