142 EQUINE ANATOMY. 



Auricular mass. — This has three faces, a superior 

 with the openings of the anterior vena cava and azy- 

 gos in front, and pulmonary veins behind ; right face 

 with the openings of the posterior vena cava, coronary 

 and brachial veins ; and a left face embracing the aorta 

 and pulmonary arteries. Its extremities are anterior 

 ciud posterior, its base resting on the ventricular mass. 



Internal aspect. — Cardiac septum divided into au- 

 ricular, with the cicatrix of the foramen of Botal ; and 

 ventricular much thicker. The right ventricle has 

 two walls, known as anterior and posterior. They have 

 fleshy columns of three kinds ; an apex, not extending 

 to the point of the heart ; a base, with the pulmonary 

 opening furnished with sigmoid valves, and the auri- 

 culo-ventricular opening presenting the tricuspid valve 

 secured by its borders to ventricular walls by the cordse 

 tendinosse. 



The right auricle presents an anterior cul de sac 

 furnished with fleshy columns of the second and 

 third kinds : a posterior wall showing the fossa ovalis, 

 an external wall with venous openings, and internal 

 wall smooth, a superior wall with venous openings, a 

 base having the auriculo- ventricular opening. 



The left ventricle has its walls covered with 

 fleshy columns ; its apex forms the point of the heart ; 

 the base presents the aortic opening, with tlie sigmoid 



