THE CARDIAC VEINS. 



855 



laying them open a distinct valve, of either one or two cusps, but usually insuffi- 

 cient, will be found at their line of junction. This valve is known as the valve of 

 Vieussens. Furthermore, the walls of the sinus differ from those of the vein in pos- 

 sessing a complete layer of muscular fibres, both oblique and circular, continuous 

 with the musculature of the auricle. 



In addition to the great coronary vein, the coronary sinus also receives the 

 posterior vein of the left ventricle and the middle cardiac vein, which open into it 

 from below, and the oblique vein of the left auricle, which passes to it from above. 



Variations — The coronary sinus, as already stated, represents the left ductus Cuvieri of 

 the embryo. It varies somewhat in length, reaching in extreme cases a length of 5.4 cm. It has 

 been observed to be obliterated at its entrance into the right auricle, the great coronary vein 

 then opening into the left innominate (brachio-cephalic) vein, and, in addition to the veins 

 already noted as emptying into it, it frequently receives the marginal vein of the left ventricle. 



I. The Left Coronary Vein. — The great cardiac or left coronary vein (v. cor- 

 dis magna) (Fig. 749) begins upon the anterior surface of the heart at the apex, 

 where it anastomoses with the veins of the posterior surface, and ascends the anterior 



Fig. 750. 



-Superior vena cava 



Left pulmonary artery 



Superior left pulmonary vein 



Inferior left pulmonary vein 



Termination of left 

 coronary vein 



Circumflex brancli of left 

 coronary artery 



Left ventiicle 



Superior right pulmonary vein 

 pulmonary artery 



ior right pulmonary vein 

 Inferior vena cava 



Coronary sinus 



Right coronary vein 

 Right coronary artery 



Posterior descending branch 

 of right coronary artery 



Middle cardiac vein 



Right ventricle 



Posterior-inferior aspect of injected heart, showing blood-vessels. 



interventricular groove in company with the left coronary artery, to the anterior 

 auriculo-ventricular groove, in which it passes to the left and, curving around the left 

 border of the heart to the posterior surface, terminates by opening into the left end 

 of the coronary sinus. 



In the vertical portion of its course it receives veins from the anterior surface of 

 both ventricles, and in its course in the auriculo-ventricular groove, throughout which it 

 is embedded in the fat which usually occupies the groove, it receives a number of small 

 veins from the surfaces of both the left auricle and ventricle. Among those from the 

 ventricle there is especially to be mentioned, as larger and more constant than the 

 rest, the vena marginalis sinistra, which ascends along the left border of the heart 

 and empties into the great coronary vein shortly before its opening into the sinus 



