THE THORAX 987 



part of the great cardiac vein. It is about i inch in length, and 

 occupies a portion of the posterior part of the left auriculo-ven- 

 tricular groove. Its left extremity is continuous with the great 

 cardiac vein, and its right extremity opens into the right auricle 

 between the vestigial Eustachian valve and the auriculo-ventricular 

 orifice, the opening being guarded by the Thebesian valve. At the 

 place where the coronary sinus is continuous with the great cardiac 

 vein there is a valve, which is composed of two segments. 



The coronary sinus is the persistent terminal part of the left duct 

 of Cuvier and left lateral cornu of the sinus venosus. 



The posterior cardiac veins ascend upon the inferior surface of 

 the left ventricle, arid open partly into the coronary sinus, and 

 partly into the contiguous portion of the great cardiac vein. One 

 of them is known as the left marginal vein. 



The middle cardiac vein (more properly called the inferior inter- 

 ventricular vein), which is of large size, commences at the apex of 

 the heart, and passes along the inferior interventricular groove 

 with the descending branch of the right coronary artery. It re- 

 ceives tributaries from the adjacent surface of the right ventricle 

 and from the interventricular septum, as well as a few from the 

 left ventricle, and it opens into the right extremity of the coronary 

 sinus. 



The right or small cardiac or coronary vein occupies the right 

 auriculo-ventricular groove, in company with the right coronary 

 artery, and it opens into the right extremity of the coronary sinus. 

 It is subject to some variation, but it usually receives tributaries 

 from the contiguous parts of the right auricle and right ventricle, 

 including the anterior cardiac veins. 



The anterior cardiac veins ascend on the front of the right ventricle, 

 and open into the right cardiac vein. One of them is known as the 

 right marginal vein. 



The oblique vein of Marshall, which is a persistent part of the 

 left 'duct of Cuvier, passes downwards and inwards over the posterior 

 aspect of the left auricle, and opens into the left extremity of the 

 coronary sinus, its orifice being destitute of a valve. 



Development. — The oblique vein of Marshall represents the portion of the 

 left duct of Cuvier which adjoins the terminal part, this latter part giving rise 

 to the coronary sinus. 



Tributaries of the Coronary Sinus. — ^These are as follows : (i) the 

 great or left cardiac vein ; (2) some of the posterior cardiac veins, 

 others of these veins opening into the great cardiac vein ; (3) the 

 middle cardiac vein ; (4) the right cardiac vein ; and (5) the oblique 

 vein of Marshall. With the exception of the last-named tributary, 

 all the others are provided with valves at their terminal orifices, 

 but elsewhere they are destitute of valves. 



The smallest cardiac veins, or vence minimce cordis, also known 

 as the vencB Thebesii, are not visible upon the exterior of the heart. 

 They are very minute, and they open into the right auricle, their 

 orifices constituting some of the foramina Thebesii. Similar 



