308 



THE MECHANICS OF THE HEART 



lunar valves and continues throughout the plateau (2 to 3). It ceases 

 with the beginning of diastole, i.e., as soon as the semilunar valves are 

 closed by the high outside pressure. The early phase of systole during 



FIG. 159. SCHEMA TO SHOW ARRANGEMENT OF APPARATUS FOR DEMONSTRATING THE 



ACTION OF THE HEART VALVES. 



A, reservoir for water; H, ox heart; B and C, windows inserted in the orifices of the 

 pulmonary vein and aorta overlying the mitral and aortic valves; E, electric battery 

 and light used to illuminate ventricular cavityt P, pump by means of which water is 

 made to circulate and to close and open the valves. 



which the ventricles simply contract upon their contents without 

 actually ejecting the blood, is known as the " setting period." Its dura- 



FIG. 160. SYNCHRONOUS RECORD OF THE INTRAVENTRICULAR PRESSURE (V), AND THE 



AORTIC PRESSURE (.A) 



S, the time record, each vibration = Moo sec-! 0-5, corresponding ordinates in 

 the two curves; 1 marks the opening of the semilunar valves; 3 (or shortly after) marks 

 the closure of these valves and the beginning of diastole. (Hiirthle.) 



tion is 0.02-0.04 sec. The period of filling of the ventricles commences 

 with the opening of the auriculoventricular valves late during 

 diastole and ceases with the beginning of the next auricular systole. 



