THE HEART 143 



the right, as the front surface of the heart is made up chiefly of the right 

 ventricle and the posterior surface of the left ventricle. The coronary ves- 

 sels which supply the tissue of the heart with blood run in the furrows or 

 grooves; also the nerves and lymphatics, which are embedded in more or 

 less fatty material, are found in this groove. 



The Chambers oj the Heart. The interior of the heart is divided by a 

 longitudinal partition in such a manner as to form two chief chambers or 

 cavities, the right and the left. Each of these chambers is again subdivided 

 transversely into an upper and a lower portion, called respectively the auricle 



FIG. 134. Outline of Heart, Lungs, and Liver to Show their Relations to each other and to 

 the Chest Wall. (Heusman and Fisher's "Anatomical Outlines.") 



and the ventricle, which freely communicate. The aperture of communica- 

 tion, however, is guarded by valves so disposed as to allow blood to pass 

 freely from the auricle into the ventricle, but not in the opposite direction. 

 There are thus four cavities ; *i the heart, the auricle and ventricle of one 

 side being quite separate from those on the other, figure 135. 



The right auricle, the right part of the base of the heart as viewed from 

 the front, is a thin-walled cavity of more or less quadrilateral shape, prolonged 

 at one corner into a tongue-shaped portion, the right auricular appendix, 

 which slightly overlaps the exit of the aorta from the left ventricle. 



The interior of the auricle is smooth, being lined with the general lining 

 membrane of the heart, the endocardium. The superior and inferior venae 

 cavse open into the auricle. The opening of the inferior cava is protected 

 and partly covered by a membrane called the Eustachian valve. In the 

 posterior wall of the auricle is a slight depression called the fossa ovalis, 



