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PRINCIPLES OF VETERINARY SCIENCE 



and posterior vena cava, and in the ventral part the right auricu- 

 loventricular orifice, which leads into the right ventricle. This 

 orifice is guarded by the tricuspid valve. By means of this 

 and the other valves the blood is kept flowing in one direction. 

 The right ventricle occupies the right anterior part of the ven- 

 tricular mass, but does not reach the apex. It communicates 



Musculi pectinati 



Aortic valve ^ 



Great coronary K J 

 vein 

 Left coronary _ 

 artery 



Bicuspid valve 



Chorda? lendi 

 Papillary muscle 



usculi pectinati 



m. 



V I '--Right coronary 

 0|/ artery 



/ -Tricuspid valve 

 ''-Papillary muscle 



Trabecule cameos 



Fig. 41. — Section of heart of horse. The section is cut nearly at right angles 

 to the ventricular septum, and is viewed from the right. (Sisson, Anatomy of 

 Domestic Animals.) 



with the pulmonary artery through the pulmonary orifice, which 

 is guarded by the semilunar valve composed of three cusps. The 

 left auricle forms the posterior part of the base of the heart. 

 Seven or eight pulmonary veins open into this cavity. Be- 

 low, it communicates by the left auriculoventricular orifice, 

 which is guarded by the bicuspid valve, with the left ventricle. 

 The left ventricle discharges blood through the aortic orifice. 

 This opening is guarded by the aortic semilunar valve similar to 

 but stronger than the corresponding valve on the right side. All 



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