34 UNIVERSITY OF MISSOURI STUDIES 



orifice may have been pushed to the left by the distention 

 of the lower part of the right auricle (Plates X and XI). 

 In this connection it will be noted that the left dome of 

 the diaphragm is at nearly the same height as the right 

 one. It is possible that the adhesions of the left lung to 

 the pericardium and diaphragm, the moderate distention of 

 the stomach and the intraperitonaeal injection may have 

 raised the left dome of the diaphragm and carried the 

 apical portion of the heart upward to a position higher 

 than it originally occupied. However, it is not probable 

 that these factors will account for the base of the heart 

 and the arch of aorta being higher than usual. 



AORTA AND VENAE CAVAE 



The aorta lies entirely to the left of the midplane at 

 its origin from the left ventricle behind the third left ster- 

 nochondral articulation. The ascending aorta inclines to 

 the right as it goes upward so that the base of the innom- 

 inate artery is to the right of the midplane behind the first 

 sternochondral articulation. The aortic arch lies behind 

 the left half of the manubrium at the level of the disc be- 

 tween the third and fourth thoracic vertebrae, and the up- 

 per half of the fourth vertebra. Its highest point is less, 

 than 1 cm. below the upper border of the sternum. The 

 artery reaches the left side of the vertebral column at the 

 level of the fifth vertebra and remains in close relation 

 with the left anterior aspect of the vertebral column down 

 to the point of bifurcation over the disc between the third 

 and fourth lumbar vertebrae (Plates VIII to XIX and 

 XXVIII, XXIX, XXXI, XXXII, XXXIII and XXXV). 



At its origin the aorta is in contact with the conus 

 arteriosus anteriorly, with the left auricula and auricle to 

 the left and posteriorly, and with the right auricle to the 



