CAVITIES OF THE HEART. 197 



advice, to expose a patient to cold during that disease, 

 since any chill is then especially apt to set up pericarditis. 

 In the earlier stages of pericardiac inflammation the rub- 

 bing surfaces on the outside of the heart and the inside of 

 the pericardium become roughened, and their friction pro- 

 duces a sound which can be heard with a stethoscope. In 

 later stages great quantities of liquid may accumulate in 

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



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

 diagram, Fig. 57, p. 194) it is found to be subdivided by a 

 'longitudinal partition or septum into completely separated 

 right 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 por- 

 tion into which veins open, known as the auricle, and a 

 thicker apical portion from which arteries arise and called 

 the ventricle. The heart cavity thus consists of a right 

 auricle and ventricle and a left auricle and ventricle, each 

 auricle communicating by an auriculo-ventricular orifice 

 with the ventricle on its own side; there is no direct com- 

 munication whatever through the septum between the op- 

 posite sides of the heart. To get from one side to the other 

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



Why should a person with rheumatic fever never be 'exposed 

 to cold except under skilled advice? What can be heard with a 

 stethoscope in the early stages of pericarditis? What may occur in 

 its later stages? 



What is seen on opening the heart? In what direction does the 

 septum run? What is an auricle? A ventricle? Enumerate the 

 Chambers of the heart cavity. With what does each auricle com- 

 municate? Is there a direct connection between the right and left 

 sides of the heart? What must the blood do to get from one side of 

 the heart to the other? 



