RIGHT AURICLE. 477 



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 descrip- 

 tion 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 anatomists, 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 prin- 

 cipal cavity or sinus, and an appendix auriculae. The interior of the sinus 

 presents for examination five openings ; two valves ; two relicts of foetal 

 structure; and two peculiarities in the proper structure of the auricle 

 They may be thus arranged : 



Openings 



Superior cava, 

 Inferior cava, 

 Coronary vein, 

 Foramina Thebesii, 

 Auriculo-ventricular opening. 



, T , ( Eustachian valve. 



Vdves ...... I Coronary valve. 



,. f. . , , ( Annulus ovalis, 

 Relicts of fatal structure Fosa 



. j ( Tuberculum Loweri, 



Structure of the auncle . j Muscul; pectinad _ 



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 through the lower and posterior wall, close to the partition 

 between the auricles (septum auricularum). The direction of these two 

 vessels is such, that a stream forced through the superior cava would be 

 directed towards the auriculo-ventricular opening. In like manner, a 

 stream rushing upwards by the inferior cava would force its current against 

 the septum auricularum ; this is the proper direction of the two currents 

 during foetal life. 



The Coronary vein returns the venous blood from the substance, of the 

 heart ; it opens into the auricle between the inferior cava and the auriculo- 

 ventricular opening, under cover of the coronary valve. 



The Foramina Thebesii* are minute poxe-like openings, by which the 

 venous blood exudes directly from the muscular structure of the heart into 

 the auricle, without entering the venous current. These openings are also 

 found in the left auricle, and in the right and left ventricles. 



* Adam Christian Thebesius. His discovery of the openings now known by hit 

 name is contained in his "Dissertatio Medica de Circulo Sanguinis in Corde," 1708. 



