I4O 



THE PERICARDIUM. 



fifth and sixth ribs. A healthy heart is about the size 

 of the clenched fist of its owner. 



14. Interior of the Heart. When the heart is cut open 



(Fig. 38) it is found to 

 be hollow. Its cavity is 

 not single, but is sepa- 

 rated into a right and a 

 left chamber, by a parti- 

 tion which runs through 

 it from base to apex. 

 Each chamber consists of 

 an upper division, Au, 

 Au', called an auricle ; 



FIG. 3 8.-Diagram of a section through and a lower division, Vi 

 the heart. Au, Au', auricles; K, V , ven- . . 

 tricles; cs, upper hollow vein; , lower hoi- V , named ^Ventricle. On 

 low vein; /*, pulmonary artery; pd, ps, pul- 

 monary veins; A, aorta. Between each each Side there IS a large 

 auricle and the corresponding ventricle, 



and at the mouth of pulmonary artery and opening between the au- 

 aorta, the valves which control the direc- 



tion of the blood-flow are seen. r j c j e an( J ventricle; but 



there is no direct passage from the cavities on the right 

 side of the heart to those on the left. 



The divisions of the heart are, therefore, right auricle, 

 right ventricle, left auricle, left ventricle. 



15. The Pericardium. The heart is surrounded by a 

 loosely fitting case or bag, named the pericardium. The 

 inside of this bag and the outside of the heart are covered 

 by a very smooth membrane. In the space between the 

 heart and its case there is in health a small quantity of 



14 How is the cavity of the heart divided ? Of what do its cham- 

 bers consist ? What is said of communication between auricles and 

 ventricles of the same and of different sides? Name the divisions of 

 the heart? 



15. What is the pericardium ? What is found inside it and outside 

 the heart ? In the space between? Use? 



