

262 A MANUAL OF ANATOMY. 



is inclined from above downward and outward. The Left : 

 Is a small oval space half an inch by an inch, its centre an 

 inch and a quarter to the left of the median line behind the 

 second left space and third cartilage. Its long axis is 

 directed from above downward and outward. 



(8) The auriculoventricular groove is indicated by a line 

 from the right to the left heart border, beginning on a level 

 with the upper margin of the fourth right and ending on a 

 level with the lower edge of the third left cartilage. This 

 line is convex upward and crosses the middle of the ster- 

 num on a level with the lower border of the third cartilages. 



(9) The aortic area is a little more than an inch wide and 

 two inches in length. It extends from the upper border 

 of the third to behind the middle of the first cartilages. At 

 its beginning and ending its centre is behind the median 

 line, but in the middle of its course the artery is convex 

 toward the right. 



(10) The Area of the Pulmonary Artery. About an inch 

 and a quarter wide and an inch and a half long (in the photo- 

 graph). Begins on a level with the lower border of the 

 third, and ends behind the middle of the second left carti- 

 lages. Below, its centre is half an inch, and above, three- 

 quarters of an inch, to the left of the median line. 



(n) The superior vena cava is represented by a vertical 

 area three-fourths of an inch wide at the right of the aortic 

 area, reaching from the (right auricle) right extremity of the 

 base line upward to the first intercostal space, where the 

 innominate veins coalesce. 



(12) The outline of the lungs (in inspiration) is indicated 

 by the following lines : 



The apices of the lungs reach into the base of the neck 

 a distance of from one and a half to two inches above the 

 first ribs, consequently the lines representing the apices of 



