26 



TOPOGRAPHICAL ANATOMY OF THE 



separated from the much larger ventricles by the coronary groove 

 (sulcus coronarius), which is continuous round the heart except where 

 interrupted by the pulmonary artery. The groove is generally largely 

 occupied by fat ; consequently its depth cannot be properly estimated 

 in the undissected organ. Externally the distinction between the right 

 and left atria is indifferently marked except on the left side. The 

 common atrial mass is crescentic in form, the horns of the crescent 



A. pulmonalis (branches of). 



Aorta. ,\^ V. azygos. 



/ 



Truncus brachiocephalicus. 



Vena cava cranialis. 



Vv. pulmonales. 

 \'ena cava caudalis 



Right atrium. 



A. coronaria dextra. 



V. cordis media. 

 Left ventricle 



Right ventricle. 



Fig. 10.— The heart and great blood-vessels as seen from the right. 



being two free projections, the auricuke ^ cordis, separated from each 

 other by the pulmonary artery and aorta. 



The ventricular part of the heart is responsible for the conical shape 

 of the organ as a whole. Its base is connected with the atria, while its 

 apex forms the apex of the entire organ. The common mass of the 

 ventricles presents two surfaces and two borders. The right surface is 



1 A uricula (dim. of atiris) [L.], the external ear, tlie lobe of the ear. The term is 

 applied to part of the atrium because of its ear-like shape. 



