4 o8 



ELEMENTAR Y ANA TOMY. 



[LESS. 



by cords (chordce tendinecz), as described in the " Elementary 

 Physiology," Lesson II. 10. 



The left auriculo-ventricular opening is guarded by two 

 flaps, forming what is called the mitral valve, from a fancied 

 resemblance to a bishop's mitre. 



The right auricle has on its left wall an oval depression 

 called the fossa ovalis, and above and below this depression 

 it receives blood from two large veins termed respectively the 

 vena cava superior and inferior. Extending upwards from 

 the margin of the opening of the last-named vessel to the 

 fossa ovalis is a rudimentary fold of membrane termed the 

 Eustachian valve. No other valve guards the entrance 

 from the venae cavae into the auricle. 



FIG. 355. I. THE LEFT SIDE, AND II. THE RIGHT SIDE OF THE HEAKT 

 DISSECTED. 



I. LA, the left auricle ; PV, the four pulmonary veins ; cd, a style passed through 

 the auriculo-ventricular aperture ; MV, the mitral valve; ah, a style passed 

 through the left ventricle into the aorta ; RA, RV, parts of the right side ol 

 the heart ; PA, pulmonary artery. 



II. RA, the right auricle ; VCS, superior vena cava ; VCI, inferior vena cava, 

 the styles./*?, cd, being passed through them into the auricle ; ab, style passed 

 through the auriculo-ventricular aperture; TV, tricuspid valve; RV, right 

 ventricle ; SL, semi-lunar valves at the base of PA, the pulmonary artery, 

 through which the style gh is passed ; LA, LV, auricle and ventricle of the 

 left side of the heart. 



The right ventricle, besides the opening between it and the 

 right auricle, has, at its upper part, another orifice ; namely, 



