136 Anatomy Applied to Medicine and Surgery. 



Landmarks, (Fig. 7). To map out the heart on the 

 walls of the chest, begin about an inch from the sternum, 

 along the lower border of the left second costal catilage, 

 and draw a line obliquely across the sternum, to terminate 

 at the upper border of the third right cartilage, about half 

 an inch from the sternum. This represents the line for the 

 base of the heart, whereas, the apex is situated about one 

 and a half inches below and three-quarters of an inch in- 

 ternal to the nipple, or, in the left fifth interspace, three 

 and a half inches from the middle of the sternum. The 

 line for the lower border, i.e., the portion that is seen 

 to rest on the diaphragm, when viewed from the front, is 

 drawn from the junction of the seventh right costal car- 

 tilage with the sternum, as far as the apex. The outline 

 for the right side corresponds to a line joining the right 

 extremity of the base-line to the right extremity of the 

 line for the lower border, and so curved that it extends 

 one and a half inches to the right of the middle line of the 

 sternum ; while the remaining part of the outline, i.e., the 

 left border, 'is represented by a curved line situated inter- 

 nal to the nipple and joining the left extremity of the base 

 line to the apex of the heart. To indicate the cavities on 

 the anterior surface of the heart, it is necessary to identify 

 the separating grooves, and this may be done as fol- 

 lows : The anterior auriculo-ventricular groove is repre- 

 sented by a line drawn from the junction of the third left 

 costal cartilage with the sternum, and passing obliquely 

 downwards to the right, to terminate at the junction of 

 the seventh right cartilage with the sternum. This groove 

 is not permanently fixed, since it is carried to the left in 

 systole and to the right in diastole, on account of the right 

 auricle becoming nearly twice as wide, in the former as 

 in the latter condition. The line for the interventricular 

 groove starts at the junction of the third left rib with its 



