THE HEART BEAT. 



545 



carotid or subclavian artery, or through the left auricle or ventricle. 

 The sound is then connected to a suitable recording apparatus by 

 rigid tubing filled with liquid. The changes in pressure in the 

 ventricle are extensive and very rapid. To register them accu- 

 rately the recording instrument must respond with great prompt- 

 ness and at the same time must be free from inertia movements. 

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

 since the heavy mass of mercury could not follow accurately the 

 quick changes in pressure. The recording manometer devised 

 by Hiirthle* has been used for this purpose, as also the optically 

 recorded movements of the more accurate segment-capsule of 

 Frank (p. 494) . A typical curve obtained by means of the Hiirthle 



Fig. 232.— Simultaneous curves of intraventricular pressure and subclavian pressure; A' 

 and A" show relative positions. The time curve indicates one-fifth sec; 2-3, the isoruetric 

 period; 3, opening of semilunar valves; 3-5, the ejection period; 5, beginning of ventricular 

 diastole; b-e, the ejection period as it affects the subclavian pressure; /, closure of the semi- 

 lunar valves; e-f, the incisura, the fall of pressure at the beginning of diastole which occasions 

 the closure of the semilunar valves. — (From Wiggers.) 



manometer is given in Fig. 231, V, and two curves as obtained 

 from an optical manometer (Wiggers) in Fig. 232. (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 con- 

 traction, 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. 231) is determined by simul- 



* Hiirthle, " Archiv f. d. gesammte Physiologie," 49, 84, 1891. 

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