38 THE MECHANISM OF THE CIRCULATION. 



origin as the waves seen on the plateau of the intraventricular pressure 

 curve. 



The moment when the sernilunar valves open can be marked on 

 the impulse curve by synchronously recording the carotid pulse, and 

 deducting the time spent in the transmission of the pulse wave. The 

 commencement of the upstroke of the pulse curve after the necessary 

 deduction marks the beginning of the systolic output when the valves 

 open (see Fig. 25). 1 By Edgren 2 and Martins 3 this moment is placed 

 at the top of the ascent of the impulse curve, where the plateau com- 

 mences. By signalling the position of the first sound on the impulse 

 curve, the moment of closure of the auriculo- ventricular valves is 

 obtained with sufficient accuracy. All these points are marked in the 

 accompanying figure 



FIG. 26. Simultaneous records of carotid pulse and heart impulse. -Edgren. 

 i, the auricular systole. 



a, the commencement of ventricular systole, the time of occurrence of the first 



sound. 



b, the opening of the semilunar valves. 



c, d, waves on the top of the plateau. 



e, the closure of the semilunar valves and commencement of diastole. 



/, the tension of the semilunar valves and the occurrence of the second sound. 



From these points the following time periods can be arrived at in man : 

 a-b, The time of rising tension in the ventricle ; a-c, the period of ven- 

 tricular contraction ; b-e, the period of output of blood ; a-/, the time 

 between the commencement of the two heart sounds ; e-a, the period of 

 diastole of the ventricles. 



Beyond these data, it must be remembered that the impulse curve 

 tells nothing of value, for the form of the curve bears no accurate 

 relation to the contraction of the heart. 



In a man with a pulse frequency of 70, Edgren determined the 

 duration of systole to be 0-379 sec., of diastole 0483 sec. The relation 

 between the duration of the systole and the frequency is shown in the 

 following table : 



Pulse Frequency. Duration of Systole. 



74- 94 0-327-0-301 sec. ) ~ , 4 



63-124 0-382-0-199 f Donders - 4 



55- 65 0-300-0-327 ) T -, . 5 



55-113 0-346-0-190 " } Landois ' 5 



47-128 0-347-0-256 Thurston. 6 



1 Hiirthle, Arch. f. d. ges. Physiol., Bonn, 1891, Bd. xlix. plate viii. fig. a. 



2 Skandin. Arch.f. Physiol., Leipzig, 1889, Bd. i. S. 127. 



3 Ztschr.f. Tclin. Med., Berlin, 1888, Bd. xiii. S. 346. 



4 Dublin Jonrn. Med. Sc., 1868, p. 225. 



5 ''Die Lehre vom Arterienpuls," S. 307. 



6 Journ. Anat. and Physiol. , London, 1876, p. 499; cf. on the time relations of the 

 cardiac movements in man, Gibson, Ibid., 1879, vol. xiv. p. 234. 





