RIGHT AURICLE. 533 



Eustachian valve, 



tf-i i 



Coronary valve. 



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 Tkebesii* are minute pore-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. 



The Auriculo-ventricular opening is the large opening of communica- 

 tion between the auricle and ventricle. 



The Eustachian^ valve is a part of the apparatus of fcetal circulation, 

 and serves to direct the placental blood from the inferior cava, through 

 the foramen ovale into the left auricle. In the adult it is a mere 

 vestige and imperfect, though sometimes it remains of large size. It 

 is formed by a fold of the lining membrane of the auricle, containing 

 some muscular fibres, is situated between the opening of the inferior 

 cava and the auriculo-ventricular opening, and is generally connected 

 with the coronary valve. 



The Coronary valve is a semilunar fold of the lining membrane, 

 stretching across the mouth of the coronary vein, and preventing the 

 reflux of the blood in the vein during the contraction of the auricle. 



The Annulus ovalis is situated on the septum auricularum, opposite 

 the termination of the inferior cava. It is the rounded margin of the 

 septum, which occupies the place of the foramen ovale of the foetus. 



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

 his name is contained in his " Dissertatio Medica de Circulo Sanguinis in 

 Corde," 1/08. 



t Bartholomew Eustachius, born at San Severino, in Naples, was Professor 

 of Medicine in Rome, where he died in 15/0. He was one of the founders of 

 modern anatomy, and the first who illustrated his works with good engravings 

 on copper. 



