ANATOMY OF THE HORSE. 
663 
whereas the ventricles are of a dull red or deep flesh colour, are 
smooth and even upon their surfaces, and of themselves compose 
three-fourths of the organ. 
The right auricle , generally found full of blood after death, is 
lined by a fine, vascular membrane, and presents internally a 
polished surface, the regularity of which is interrupted in places 
by many fleshy prominences, named the musculi pectinati; be¬ 
tween which are numerous little sinuses, or cul-de-sacs , that, as 
well as the fleshy pillars themselves, vary much in size, and are 
most numerous and remarkable within the appendix , or ear-like 
portion of the auricle, where they form together a reticulated 
structure. Three venous trunks terminate in this cavity: the 
vena cava anterior opens into the superior and posterior part of it; 
the vena cava posterior opens into the inferior and posterior part; 
and the coronary vein j ust below it. The vena azygos forms a 
junction with the anterior cava just as the latter pierces the auri¬ 
cular parietes. Between the openings made by the two venae 
cavae, there is a prominence that is usually called the tuberculum 
Loweri. There is a deep sac or sinus at the entrance of the pos¬ 
terior cava; and between this and the mouth of the coronary 
vein, a crescentic valvular flap, which projects half way over the 
mouth of the latter vessel. The right auricle has a free commu¬ 
nication with the right ventricle by an aperture of large size, 
called the auriculo-ventricular opening . 
One auricle is divided from the other by a muscular partition, 
denominated the septum auricularum; in which may be seen, 
when the part is held to the light, an elliptical inlet of semi¬ 
transparent membrane, crossed in places by fleshy fasciculi, which 
takes the name of fossa ovalis: in some subjects there is a small 
aperture through it, and this is all that remains of the foramen 
ovale . 
The right ventricle is redder and considerably thicker in sub¬ 
stance than the right auricle : like it, it commonly contains, after 
death, a large coagulum of blood. It is likewise lined by a 
smooth, polished membrane, and has within it numerous fleshy 
pillars , which, instead of being reticulated as those are in the 
auricle, are disposed longitudinally. In addition to these, there 
are three conspicuous fleshy prominences, from their size named 
the carnece columnce , from which several little tendinous cords, 
cordcc tendinecc , proceed to the edges of three membranous and 
fibrous productions (sometimes distinguished by the name of Cor¬ 
tina tendineaj that close the auriculo-ventricular opening: the ap¬ 
paratus altogether forms the valvula tricusp is. Other cords, similar 
to the cordae tendineae, but stronger than they, pass between the 
outer wall and the septum. The pulmonary artery emerges from 
