548 CIRCULATION OF BLOOD AND LYMPH. 



A mercury manometer, for instance, would be entirely useless for 

 such a purpose, since the heavy mass of mercury could not follow 

 accurately the quick changes in pressure. The recording manom- 

 eter devised by Hiirthle (p. 495) has been used very frequently 

 for this purpose, as also somewhat similar instruments in which 

 the vibrations of the tambour membrane are recorded photo- 

 graphically by placing a small mirror on the membrane and reflect- 

 ing a beam of light from it (optical manometer) . A typical curve 

 obtained by means of the Hiirthle manometer is given in Fig. 

 230, V, and two curves as obtained from an optical manometer 

 (Wiggers) in Fig. 230a. (Consult also the classical curve obtained 

 by Chauveau and Marey from the heart of the horse [Fig. 220].) 

 It will be seen that the pressure in the heart rises suddenly with the 

 beginning of the ventricular contraction, and a certain time elapses 

 before this pressure is great enough to open the semilunar valves. 

 The moment that this occurs (1, on the ventricular curve in 

 Fig. 230) is determined by simultaneous measurement of the pres- 

 sure in the aorta, it being evident that the pressure will begin to 

 rise in this latter vessel the moment that the valves open. The 

 different features of the ventricular systole as gathered from these 

 pressure curves are expressed by Hiirthle* as follows: 



I. Systole, phase of contraction of the muscle fibers (0 to 3 in Fig. 230, V) . 



(a) Period of tension (0 to 1), during which the auricula-ventricular and 

 semilunar valves are both closed and the heart muscle is squeezing 

 upon the contained blood. This period ends at the opening of the 

 semilunar valves. 



(6) Period of emptying (1 to 3). During this time the heart is empty- 

 ing itself into the aorta and the intraventricular pressure remains 

 above aortic pressure. It ends with the cessation of the contrac- 

 tion of the muscle and the beginning of tho rapid relaxation. 

 II. Diastole, phase of relaxation and rest of the muscle fibers. 



(a) Period of relaxation from 3 until the curve reaches a horizontal. 

 At the beginning of the relaxation the semilunar valves are closed, 

 and from comparison with the aortic curve the instant of the occur- 

 rence of this closure is placed shortly after 3. 



(6) Period of filling. This period begins as soon as the auriculo- ventric- 

 ular valves open and the stream of blood, which had been flowing 

 into the auricle throughout the ventricular systole, is permitted to 

 enter the ventricle. During this period of filling the ventricular 

 pressure rises slightly as thelieart becomes turgid with blood. This 

 increase of pressure is indicated in most cardiograms by a gradual 

 rise of the curve during this period. It is shown in the curve of 

 Chauveau and Mary, given in Fig. 220. 



A feature of the intraventricular pressure curve that has been 

 much discussed is the flattened top, or plateau, exhibited in Fig. 

 230. f According to some authors a period of even pressure of 

 this kind is an artefact due to imperfection in the recording instru- 

 ment. They claim that with an adequate instrument the pressure 



"Hiirthle, "Archiv f. d. gesammte Physiologic," 49, 84, 1891. 

 t For discussion, see Tigerstedt, "Skandinavisches Archiv f. Physiol.," 

 28, 37, 1912; also Wiggers, "American Journal of Physiology," 33, 382, 1914, 



