13: 



THE ANATOMY OF THE HORSE. 



Directions. — The left ventricle should be opened by an incision 

 similar to that used on the right side. The point of the scalpel should 

 be passed through the wall of the ventricle near the upper end of the 

 left ventricular furrow, and the incision should be carried down the 

 left £ide of the ventricle, round the apex, and up the right side to 

 within a short distance of the auriculo- ventricular groove, the cut being 

 made near the septum, to which the ventricular furrows will serve as a 

 guide. 



; The Cavity of the Left Ventricle is longer than that of the right, 

 and is almost conical in shape, the base being at the auriculo-ventri- 

 cular opening. On transverse section it gives an oval or nearly circular 

 outline, the septum, as well as the wall of the ventricle, being concave 

 towards the cavity. It will be observed that its wall is about thrice 

 the thickness of that of the right cavity, a circumstance which makes 



Fig. 13. 



Root of the Common Aorta laid open. 



1,1,1. Semilunar segments of the aortic valve ; 2. Corpus Arantii ; 3, 3. Orifices of right and left 

 ' coronary arteries from two of the sinuses of Valsalva ; 4. Ventricular wall ; 5. Arterial wall. 



it easy to distinguish the right and left ventricles in the undissected 

 heart ; for, whereas the former appears flabby, the latter is firm and 

 solid-looking. The left ventricle possesses columnar, carnece like those on 

 the right side. The musculi papillares are two in number, and are of 

 very large size. They are placed on the wall, and are provided with 

 chorda? tendinece stronger than those of the right cavity. The base of 

 the cavity shows the left auriculo -ventricular opening, which is somewhat 

 smaller than the right. It is guarded by a valve with two large cusps, 

 and hence called the bicuspid valve. It is also very commonly 

 designated the mitral valve, from a fancied resemblance to a bishop's 

 mitre. The jfusps are stronger than those of the tricuspid valve, with 

 which they agree in shape and disposition. Two smaller segments 

 alternate with the main ones. In mode of action the mitral exactly 

 resembles the tricuspid valve. When the ventricle contracts, the blood, 



