THORAX 



the information he has gained regarding the relationship of 

 the apex of the heart and the borders of the sterno-costal 

 surface of the heart to the anterior wall of the thorax. The 

 upper border is formed by the atria, and as the heart lies in 

 situ it is concealed to a great extent by the aorta and the 



FIG. 26. The relations of the Heart and of its Orifices to the Anterior 

 Thoracic Wall. (Young and Robinson.) 



to VII. Costal cartilages. 



A. Aorta. 

 Ao. Aortic orifice. 



C. Clavicle. 

 LA. Left atrium. 

 LV. Left ventricle. 



M. Mitral orifice. 



P. Pulmonary orifice. 



RA. Right atrium. 



RV. Right ventricle. 



SVc. Superior vena cava. 



T. Tricuspid orifice. 



pulmonary artery. Its position is marked on the surface 

 by a line extending from the lower border of the second 

 left to the upper border of the third right costal cartilage, 

 commencing and terminating about half an inch from the 

 border of the sternum. The right border is formed entirely 

 by the right atrium, and its position is indicated on the sur- 



