678 THE VEINS. 



great 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 veins join- 

 ing this vessel, excepting the oblique vein above mentioned, are provided with 

 valves. 



The Venae 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. Similarly minute veins are said to open into the left auricle and both 

 ventricles. 



