THE VESSELS. 291 



cavity is formed by three walls, an anterior convex, an internal (the septum), 

 and a larger posterior, concave. It presents in the adult three, in the foetus 

 four openings. 



a. The crescentic opening of the superior cava, separated by a fasciculus of 

 muscle from the appendix on the left, from the inferior cava on the right, 

 without valves, looks downwards and rather backwards. 



b. The crescentic opening of the inferior cava, larger than the former, close 

 to the septum, not vertical from below upwards, but directed obliquely (at a 

 right angle to the vein), with the half-rnoon-shaped valvula Eustachii on the 

 anterior border, which completely closes the opening in the embryo only. 

 The free concave border of the Eustachian valve looks upwards, the attached 

 convex downwards. 



c. The opening of vena magna cordis [coronary vein] lies before the last 

 described, separated from it by the Eustachian valve ; is closed by a thin, 

 crescentic valve, valvula Thebesii, the superior extremity of which continues 

 into the inferior of the valv. Eustack. 



Several small/oramma Thebesii are found below the opening of the supe- 

 rior cava, but they are not to be considered as the openings of smaller cardiac 

 veins. 



d. Foramen ovale, in the embryo, is a longitudinal opening in the posterior 

 inferior part of the septum between the auricles. At birth is already found 

 in its place a smooth or wrinkled, but thin layer, fossa ovalis, bordered above 

 and before by a crescentic, fleshy protuberance, isthmus Vieussens, the inferior 

 extremity of which passes into the Valv. Eustachii. A depression with a 

 small foramen is frequently found in the oval fossa behind the isthmus, as the 

 remains of the oval foramen. 



Valvula foramin. ovalis (of the fetus) is the membranous portion spread 

 out in the circle of Vieussens, the continuation of the inner coat of the left 

 circumference of ven. cava super., whilst the valvula Eustachii proceeds from 

 the right circumference. 



Tuberculum Loweri, the elevation at the upper part of septum atriorum, 

 between the mouth of v. cava sup. and fossa ovalis, which directs the stream 

 of blood from v. cava sup. upon the posterior inferior circumference of the 

 right auricle, and that of v. cava infer, forwards, and to the right towards the 

 right appendix. 



2. Right ventricle, ventriculus dexter., pulmonary ventricle, at the anterior 

 inferior part of the heart, directed obliquely to the left and downwards from 

 its auricle, does not reach the extreme apex. Its internal wall (septum ven- 

 tricular.,) is convex, and on its lower half like trellis- work. The anterior and 

 inferior walls are concave, thin and loose, and beset with an interlacement of 

 fleshy fasciculi (mm. papillares), as they are found, also, particularly deve- 

 loped in the cavities of the auricles. At its base the two following openings 

 are found : 



a. Right auricular-ventricular opening, ostium venosum, at the posterior, 

 right part of the base of the ventricle, is elliptical (from before to behind), six- 



