214 



1HE HUMAN BODY. 



FIG. 89. Diagram representing a section 

 through the heart from base to apex. 



the outside of the heart and the inside of the pericardium 

 become roughened, and their friction produces a sound 

 which can be recognized through the stethoscope. In later 

 stages great quantities of liquid may accumulate in the peri- 

 cardium so as to seriously impede the heart's beat. 



The Cavities of the Heart. On opening the heart (see 

 diagram Fig. 89) it is found to be subdivided by a longi- 

 tudinal partition or sep- 

 tum into completely sepa- 

 rated rigl\t and left halves,- 

 the partition running from 

 about the middle of the 

 base to a point a little on 

 the right of the apex. 

 Each of the chambers on 

 the sides of the septum is 

 again incompletely divided 

 transversely, into a thinner 

 basal portion into which 

 veins open, known as the 

 auricle, and a thicker apical portion from which arteries 

 arise, called the ventricle. The heart thus consists of a right 

 auricle and ventricle and a left auricle and ventricle, each 

 auricle communicating by an aunculo-ventricular orifice 

 with the ventricle on its own side, and there is no direct 

 communication whatever through the septum between the 

 opposite sides of the heart. To get from one side to the 

 other the blood must leave the heart and pass through a set 

 of capillaries, as may readily be seen by tracing the course of 

 the vessels in Fig. 87. 



The Heart as seen from its Exterior. When the heart 

 is viewed from the side turned towards the sternum (Fig. 90) 

 the two auricles, Aid and As, are seen to be separated by a 

 deep groove from the ventricles, Vd and Vs. A more 

 shallow furrow runs between the ventricles and indicates the 

 position of the internal longitudinal septum. On the dorsal 

 aspect of the heart (Fig. 91) similar furrows may be noted, 

 and on one or other of the two figures the great vessels 

 opening into the cavities of Utes heart may be seen. The 

 pulmonary artery, P, arises from the right ventricle, and 

 very soon divades into the right and left pulmonary arteries, 

 Pd and Ps, which break up into smaller branches and enter 



