OPENINGS OF THE HEART. 471 



vessel at the root of the heart ; it crosses obliquely the commence- 

 ment of the aorta. The heart consists of two auricles and two 

 ventricles, which are respectively named, from their position, right 

 and left. The right is the venous side of the heart ; it receives into 

 its auricle venous blood from every part of the body, by the superior 

 and inferior cava and coronary vein. From the auricle the blood 

 passes into the ventricle, and from the ventricle through the pul- 

 monary artery, to the capillaries of the lungs. From these it is 

 returned as arterial blood to the left auricle ; from the left auricle 

 it passes into the left ventricle ; and from the left ventricle is carried 

 through the aorta, to be distributed to every part of the body, and 

 again returned to the heart by the veins. This constitutes the course 

 of the adult circulation. 



The heart is best studied in situ. If, however, it be removed 

 from the body, it should be placed in the position indicated in the 

 above description of its situation. A transverse incision should then 

 be made along the ventricular margin of the right auricle, from the 

 appendix to its right border, and crossed by a perpendicular incision, 

 carried from the side of the superior to the inferior cava. The 

 blood must then be removed. Some fine specimens of white fibrin 

 are frequently found with the coagula ; occasionally they are 

 yellow and gelatinous. This appearance deceived the older anato- 

 mists, who called these substances " polypus of the heart :" they are 

 also frequently found in the right ventricle, and sometimes in the 

 left cavities. 



The RIGHT AURICLE is larger than the left, and is divided into a 

 principal cavity or sinus, and an appendix auriculae. The interior 

 of the sinus presents for examination five openings ; two valves ; 

 two relics of foetal structure ; and two peculiarities in the proper 

 structure of the auricle. They may be thus arranged : 



Superior cava, 

 Inferior cava, 

 Openings ...... ^ Coronary vein, 



Foramina Thebesii, 

 Auriculo-ventricular opening. 



rr , ( Eustachian valve, 



Vahes ...... j Coronary valve. 



( Annulus ovalis, 

 Rehcs offcetal structure 



- ,, n . 7 ( Tuberculum Loweri, 

 Structure of the Mnde j Musculi pectinati> 



The Superior cava returns the blood from the upper half of the 

 body, and opens into the upper and front part of the auricle. 



The Inferior cava returns the blood from the lower half of the 

 body, and opens into the lower and posterior wall, close to the par- 

 tition between the auricles (septum auriculorum). The direction of 



