Superficial Cardiac Area 



165 



The superficial cardiac area is that part of the front of the heart 

 which is not separated from the chest-wall by lung. The larger the 

 lungs, the smaller that area : thus in 

 emphysema the heart may be entirely 

 covered by lung, but in phthisis, 

 where the lung-tissue is wasted, the 

 superficial cardiac area is extensive. 

 It is triangular one side of the 

 space being formed by the straight 

 margin of the right lung ; the base 

 corresponds with the flat border of 

 the heart, resting on the diaphragm ; 

 and the third side by the sloping 

 margin of left lung, behind the fourth 

 left cartilage. During systole the 

 apex of the heart displaces the little 

 tongue of lung shown in the wood- 

 cut, and impinges against the fifth 

 space. 



To mark out the superficial car- 

 diac area, draw the line, as given 

 above, from the xipho-sternal joint 

 to the apex this gives the base of 

 the space ; draw a second down the 

 mid-sternum from the level of the 

 fourth cartilage to the xipho-sternal 

 Joint, to define the margin of the 

 right lung, and a third from the top 



of this line to the apex. This border of the space usually slopes down 

 with the fourth cartilage or with the fourth space of the left side. 



The tongue of lung which laps the apex of the heart is the lowest 

 part of the upper pulmonary lobe, and it easily slips aside for the con- 

 venience of the movements of the apex of the heart. 



THE INTERIOR OF THE HEART 



The endocardium is a serous layer which lines the cavities of the 

 heart, and is continued from them along the arteries and veins. Its 

 reduplication, with some fibrous tissue intervening, forms the valves. 

 It consists of pavement cells upon a stratum of connective tissue. In- 

 flammation of the endocardium (as in acute rheumatism) may cause 

 the growth of warts upon the cardiac valves. Endocarditis generally 

 occurs on the left, the hard-worked side, of the heart, and it is often 

 secondary to pericarditis, the inflammation having traversed the mus- 

 cular wall of the heart to reach the endocardium. 



The rigrht auricle has a capacity of about two ounces. It consists 



