826 THE VASCULAR SYSTEM. 
solid viscera. The coronary sinus receives blood from the veins of the walls of the 
heart alone. 
General ea oars veins of the body wall and lmbs form two 
groups—(1) the superfic ial veins ; (2) the deep veins. 
The superficial veins, which commence in the capillaries of the skin and sub- 
cutaneous tissues, lie in the superficial fascia, and are very numerous. They 
frequently anastomose with one another, and they also communicate with the deep 
veins, in which, after piercing the deep fascia, they terminate. They may or may 
not accompany superficial arteries. ’ 
The deep veins accompany arteries, and are known as vene comites. The large 
arteries have only one accompanying vein, but with the medium-sized and small 
arteries there are usually two ven comites, which freely anastomose with each 
other by short transverse branches of communication. 
Visceral veins usually accompany the arteries which supply tite in the 
head, neck, thorax, and abdomen. As a rule there is only one vem with each 
visceral artery, and, with the exception of those which enter into the formation of 
the portal system, they terminate in the deep systemic veins. 
THE CORONARY SINUS AND THE VEINS OF THE HEART. 
The coronary sinus (sinus coronarius, Fig. 545) is a short, but relatively wide, 
venous trunk which receives the majority of the veins of the heart. It lies in the 
inferior portion of the auriculo-ventricular suleus, between the left auricle and 
the left ventricle, and it is covered superficially by some of the muscular fibres of 
the auricle. 
It terminates in the lower and back part of the right auricle, between the orifice 
of the inferior vena cava above and on the right, and the right Aucula: ventricular 
orifice below and on the left; an imperfect valve, consisting of one or two cusps, 
called the valve of Thebesius, is situated at the opening ‘of the sinus into the 
auricle. . 
The apertures of all the tributaries of the coronary sinus, except that of the 
oblique vein, are provided with valves, which, however, are frequently incompetent. 
Tributaries.—(1) The great cardiac or left coronary vein (v. cordis magna, Fig. 546) 
commences at the apex of the heart. It ascends in the anterior interventricular sulcus 
to the auriculo-ventricular groove ; it then turns to the left, and, passing round the left 
margin of the heart into the postero-inferior part of the auriculo-ventricular groove, 
terminates in the left extremity of the coronary sinus. It receives tributaries from the 
walls of both ventricles and from the wall of the left auricle. It also receives the left 
marginal vein, which commences at the lower extremity of the left margin of the heart, 
along which it ascends to its termination. 
(2) Small cardiac or right coronary vein (v. cordis parva).—This vein is very vari- 
able; as a rule it commences at the right margin of the heart in the auriculo-ventricular 
sulcus, passes to the left, and terminates in the coronary sinus near its right end. It 
receives tributaries from the walls of the right auricle and the right ventricle ; one from the 
latter, the right marginal vein, ascends along the right margin of the heart, and sometimes 
opens directly into the right auricle. 
(3) The oblique vein of Marshall (v. obliqua atrii sinistri, Fig. 545) is a small venous 
channel which descends obliquely on the posterior wall of the left auricle and terminates 
in the coronary sinus. Its orifice is not provided with a valve. It is of special interest, 
inasmuch as it represents the left superior vena cava of some other mammals, and is 
developed from the left duct of Cuvier. 
(4) The inferior interventricular, inferior cardiac, or middle cardiac vein (vy. cordis 
media), commences at the apex of the heart, and, passing backwards in the inferior 
interventricular sulcus, terminates in the right end, of the coronary sinus. It receives 
tributaries from the inferior parts of the walls of both ventricles. 
Veins of the heart which do not end in the coronary sinus. —(«) The anterior 
cardiac veins (vy. cordis anteriores) ave two or three small vessels which ascend on the 
anterior wall of the right ventricle to the auriculo-ventricular groove, where they 
either end separately in the right auricle or terminate in the commencement of the 
small cardiac vein. (6) The vene minime cordis—A namber of small veins which ~ 
