176 



THE CIRCULATORY APPARATUS 



(fibro-elastic) tissue. On opening the heart the 

 following structures can be seen within its cavity: 



The Right Auricle. This is larger than the left, its 

 wall being about one line in thickness and its capacity 

 two ounces. .Within the auricle the following parts 

 present themselves for examination: 



FIG. 71 



Front view of the thorax, showing relation of the heart and its valves, 

 lungs, etc., to the ribs and sternum. P, pulmonary orifice; Ao, aortic orifice; 

 M, left auriculoventricular orifice; Tr, right auriculoventricular orifice. 



The orifice of the superior vena'cava, looking downward 

 and forward. The orifice of the inferior vena cava, at 

 the lowest part, near the septum, looking upward 



