THE LUNGS 



921 



right side the anterior l)order passes obli(j[uely downwards from the apex, Ix'hind 

 the sterno-clavicular articulation, to the middle line, at the Junction of the manu- 

 I)rium with the body of the sternum (tig. 521), thence it descends vertically to the 

 lower end of the gladiolus. The lower border extends round the l)ase of the sac, 

 commencing at the lower end of the gladiolus it runs downwards and outwards 

 behind the seventh costal (iartilage, still descending it crosses the seventh, eighth, 

 and ninth ribs reaching the lower border of tlie latter in the mid-axillary line; 

 passing backwards it comes into relation with the tenth, eleventh, and twelfth ribs, 

 and ascending to the head of the latter it joins the posterior border, and then, 

 turning forwards, it passes along the groove between the pericardium and the dia- 

 phragm to its point of commencement. The posterior border extends from the 

 neck of the first rib to the head of the twelfth; it is broad and rounded. The 

 anterior border on the left side descends inwards ))ehind the sterno-clavicular artic- 

 ulation as on the right side, and reaches the middle line at the same point, then 

 it passes vertically downwards to the level of the fifth chondro-st(!rnal articulation 

 (fig. 521), from this i)oint it runs downwards and outwards behind the cartilages 



Fig. 542. — Antkrior View^ of Fcetal Heart, Vessels, and Lungs. 



SUPERIOR LOBE OF RIGHT LUNG 



Aorta 

 I'liliKiiiiiiry artery — 



RIGHT AURICULAR APPENDIX 



DUCTUS ARTERIOSUS 



'- i / 



— I'lilinonary artury 



SUPERIOR LOBE OF LEFT 

 LUNG 



LEFT AURICULAR APPENDIX 

 Piihnonary artery 



INFERIOR LOBE 

 4— Descending aorta 



of the fifth and sixth ribs to the seventh costo-chondral joint, where it join.s the 

 inferior border. The inferior Ijorder descends across the eighth, nine,, and tenth 

 ril)S to the lower l)order of the latter in the mid-axillary line, further back it crosses 

 the eleventh rib and ascends along the twelfth ril) to join the posterior lx)rder, as 

 on the right side. The general relaticms of the inner part of the lower border and 

 the whole of the posterior border are the same as on the right side. 



The lower extremity of the pleural sac does not extend to the lower extremity 

 of the thorax, laterally; therefore for a short distance the diai)hragm and the 

 lowest intercostal nniscles are in <'ontact. 



Below the root of each lung a fold of tlir i»lt'ura descends to tlu' diai)hragm, the 

 ligamentum latum pulmonis. The ))leurai sacs on each side j)ass for an inch or 

 more above the level of the anterior part of the first rib, beneath the scalene muscles, 

 covering the apices of the lungs, and the ]»arietal layer is here strengthened l»y a dome 

 of fascia which descends from beneath the nuiscles to the inner border of the first 

 rib. The interval between the two .sacs is considerable ])oth altove and below: but 

 opposite the second piece of the sternum, corresponding with the second, third, and 

 fourth rib cartilages (fig. 521), they are clo.sely approximated or in actual contact. 



The lungs are not (juite so extensive as the jileural sacs, and this is more espe- 



