690 



HUMAN ANATOMY. 



It may be regarded as possessing two surfaces, which are not, however, distinctly- 

 separated, but pass into each other with rounded edges, especially upon the left side. 

 One of these surfaces looks forward and somewhat upward, and is separated by the peri- 

 cardium and some loose areolar tissue from contact with the sternum and the lower 

 costal cartilages, the thin anterior edges of the lungs and pleurae also intervening to 

 a considerable extent; this is the antero-superior surface (fades sternocostalis), and 

 for convenience it may be more briefly termed the anterior surface. The other, the 

 postero-iiiferior or posterior surface (fades diaphragmatica), rests directly upon the 

 upper surface of the diaphragm. 



At about one-third of the distance from the base to the apex a deep circular 

 groove, more distinct upon the posterior surface, surrounds the heart, separating an 



Fig. 654. 



Superior vena cava 



Systemic aorta (aorta) 



Right auricular 

 appendage 



Right auricle 



Auriculo-ventricular 



groove 



Right ventricle 



Line of reflection of 

 pericardium 



Ductus arteriosus 



Pulmonary aorta 

 (pulmonarj' artery) 



Probe in transverse sinus 



Left auricular 

 appendage 



Conus arteriosus 



Left ventricle 



Anterior interv'entricu- 

 lar groove 



Apex 

 Anterior aspect of heart hardened in situ ; probe lies in transverse sinus of pericardium. 



upper thin-walled auricular portion of the organ from a lower thick-walled ventricular 

 one ; this groove is termed the auriculo-ventricular groove (sulcus coronarius), and 

 contains the proximal portions of the coronary vessels which supply the heart's sub- 

 stance. Extending towards the apex from this groove, two other shallower grooves 

 are to be observed, one situated towards the right side of the anterior surface and the 

 other upon the posterior surface. These grooves, which also lodge portions of the 

 coronary vessels, are the anterior and posterior interventj'iciilar grooves (sulci longi- 

 tudinales), and mark the line of separation of the ventricular portion of the heart into 

 two chambers known as the I'ight and left ventricles. From the base of the right ven- 

 tricle a large blood-vessel, thepulino7iary aorta ox pulmonary ajiery, arises, while from 

 the base of the Jeh ventricle, and almost immediately posterior to the root of the pul- 

 monary aorta, the systemic aorta takes its origin. The orifices by which each of these 



