68 



THE HEART 



the pressure just exceeds 100. for the heart is, as it were, 

 unprepared for the extra call made upon it. At this beat 

 only a part of the 8 c.c. — let us say 4 c.c. — is discharged. 



Fig. 15. — The effect of increased arterial pressure on the heart. 

 C, cardiometer ; B.P., arterial blood i^ressure; V.P., pressure in 

 inferior vena cava. — 100 and — 80 indicate height of blood 

 pressure in mm. Hg. (From Starling's Principles of Phyniology .) 



The heart at the end of systole contains 4 c.c. During the 

 subsequent diastole, another 8 c.c. flows in. To accommo- 

 date 12 c.c, the volume of the ventricle during diastole is 



