1 68 



THE CIRCULATION OF THE BLOOD 



front and in the back, separating the one from the other. The anterior groove 

 is nearer the left margin, and the posterior nearer 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 vessels which supply the tissue 

 of the heart with blood run in the furrows or sulci; also the nerves and lymph- 

 atics, which are embedded in more or less fatty material, are found in this 

 groove. 



The Chambers of 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 in 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, pro- 

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

 dix, 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 vena 

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



