454 



DISSECTION OF THE THORAX. 



downwards, slightly convex downwards, from the seventh chondro-sternal 

 articulation of the right side to the apex in the fifth left interspace 

 just below the costo-chondral junction, the latter point being usually 

 about one inch and a half below, and three-quarters of an inch to 

 the sternal side of the nipple in the male and, before child-bearing, 



to right in the female. On the right side the heart projects about one inch 

 and a half from the middle line of the sternum ; and on the left, 



and left. the apex is distant from three to three and a half inches from the 

 centre of the breast-bone. 



Superficial The portion of the heart which is uncovered by lung (the area of 



portion of 

 heart. 



FIG. 166. DIAGRAM SHOWING THE POSITION OF THE HEART TO THE RIBS 

 AND STERNUM, THE SOFT PARTS BEING REMOVED FROM THE EXTERIOR 

 OF THE THORAX. THE EDGE OF EACH LUNG is SHOWN BY A DOTTED 

 LINE. THE LEFT AURICLE EXTENDS SOMEWHAT HIGHER THAN THE 

 AREA INDICATED IN THE FIGURE, PROJECTING INTO THE SECOND 

 INTERCOSTAL SPACE. 



superficial cardiac dulness) is included between the middle line of 

 the sternum, in its lower third, and a line drawn from the centre 

 of the breast-bone between the fourth costal cartilages to the apex 

 of the heart (fig. 166). 



Chambers of Component parts. The heart is a double organ ; and in each half 

 there are two chambers, an auricle and a ventricle, which com- 

 municate together, and are provided with vessels for the entrance 

 Grooves : and exit of the blood. The surface is marked by grooves indicating 

 auric.ulo- this division. Thus, passing circularly round the heart, nearer the 



heart. 



ventricular, 



base than the apex, is a groove which cuts off the thin auricular 



