CARDIAC PULMONARY. 479 



CARDIAC VEINS. 



The veins which return the blood from the substance of the heart are the 



Great cardiac vein. Anterior cardiac veins. 



Posterior cardiac vein. Venae Thebesii. 



The Great Cardiac Vein is a vessel of considerable size, which commences at 

 the apex of the heart, and ascends along the anterior interventricular groove to 

 the base of the ventricles. It then curves to the left side, around the auriculo- 

 ventricular groove, between the left auricle and ventricle, to the back part of 

 the heart, and opens into the coronary sinus, its aperture being guarded by two 

 valves. It receives the posterior cardiac vein, and the left cardiac veins from 

 the left auricle and ventricle, one of which, ascending along the left margin of 

 the ventricle, is of large size. The branches joining it are provided with 

 valves. 



The Posterior Cardiac Vein commences, by small branches, at the apex of the 

 heart, communicating with those of the preceding. It ascends along the posterior 

 interventricular groove to the base of the heart, and terminates in the coronary 

 sinus, its orifice being guarded by a valve. It receives the veins from the posterior 

 surface of both ventricles. 



The Anterior Cardiac Veins are three or four small branches, which collect 

 the blood from the anterior surface of the right ventricle. One of these, the 

 vein of Galen, larger than the rest, runs along the right border of the heart. 

 They open separately into the lower part of the right auricle. 



The Vense Thebesii are numerous minute veins, which return the blood 

 directly from the muscular substance, without entering the venous current. 

 They open, by minute orifices, foramina Thebesii, on the inner surface of the right 

 auricle. 



The Coronary Sinus is that portion of the great cardiac vein which is situated 

 in the posterior part of the left auriculo-ventricular groove. It is about an inch 

 in length, presents a considerable dilatation, and is covered by the muscular fibres 

 of the left auricle. It receives the great cardiac vein, the posterior cardiac vein, 

 and an oblique vein from the back part of the left auricle, the remnant of the 

 obliterated left innominate trunk of the foetus, described by Mr. Marshall. The 

 coronary sinus terminates in the right auricle, between the inferior vena cava 

 and the auriculo-ventricular aperture, its orifice being guarded by a semilunar 

 fold of the lining membrane of the heart, the coronary valve. All the branches 

 joining this vessel, excepting the oblique vein above mentioned, are provided 

 with valves. 



THE PULMONARY VEINS. 



The Pulmonary Veins return the arterial blood from the lungs to the left 

 auricle of the heart. They are four in number, two for each lung. The pul- 

 monary differ from other veins in several respects: 1. They carry arterial 

 instead of venous blood. 2. They are destitute of valves. 3. They are only 

 slightly larger than the arteries they accompany. 4. They accompany those 

 vessels singly. They commence in a capillary network, upon the parietes of the 

 bronchial cells, where they are continuous with the ramifications of the pulmonary 

 artery, and, uniting together, form a single trunk for each lobule. These branches, 

 successively uniting, form a single trunk for each lobe, three for the right, and two 

 for the left, lung. The vein of the middle lobe of the right lung unites with that 

 from the upper lobe, in most cases, forming two trunks on each side, which open 



