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PHYSIOLOGY. 



walls of the right auricle arc thin and translucent, but are thickened 

 by means of isolated columns of muscle called the pectinate muscles. 

 These pectinate muscles make the interior of the heart present an 

 uneven, ridge-like appearance. On the partition between the auri- 

 cles there is a shallow, oval fossa, with a border, which is the posi- 

 tion of the foramen ovale, by which the two auricles communicated 



Fig. 62. Anterior Surface of the Heart. (BouRGERY.) 



1, Right ventricle. 2, Left ventricle. 4, Right auricle. 5, Left auricle. 

 6, Pulmonary artery 7, Aorta. 8, Vena cava superior. 9, Anterior coronary 

 artery. 10, Posterior coronary artery. 11, Coronary vein. 



during intra-uterine life. The openings of small veins, the fora- 

 mina Thebesii, can be seen at various parts of the inner surface of 

 the right auricle. 



The auriculo-ventricular orifice of the right side of the heart 

 is a large oval aperture. It is about an inch in diameter. It is 

 guarded by the tricuspid valve, or right auriculo-ventricular valve. 



