502 CIRCULATION OF BLOOD AND LYMPH. 



is partly a pressure curve and partly a volume curve, that is, the 

 changes in volume as well as the changes in pressure of the heart 

 during systole will affect the instrument. 



The Intraventricular Pressure During Systole. The best 

 analyses of the details of the systole of the ventricle have been made 

 by a study of the changes in pressure within the ventricle. For 

 this purpose a tube filled with liquid is introduced into the cavity of 

 the ventricle. A tube used for such a purpose is designated as a 

 heart-sound. For the right ventricle it is introduced through an 

 opening in the jugular vein and pushed down until it lies in the 

 ventricle. For the left ventricle it is introduced by way of the 

 carotid or subclavian artery and in this case is forced through the 

 opening guarded by the semilunar valves. 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 



Fig. 212. Synchronous record of the intra ventricular pressure (F), and the aortic 

 pressure (A): S, The time record, each vibration = ^io s ^ c - 0-5, corresponding ordi- 

 nates in the two curves; 1 marks the opening of the semilunar valves; 3 marks the 

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



and very rapid. To register them accurately the recording instru- 

 ment must respond with great promptness and at the same time 

 must be free from inertia movements. 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 manometer devised by Hiirthle (p. 

 462) seems to have met the requirements more satisfactorily than 

 any other of the numerous instruments described. Atypical curve 

 obtained by means of the Hiirthle manometer is given in Fig. 212, V. 

 (Consult also the classical curve obtained by Chauveau and Marey 

 from the heart of the horse [Fig. 207].) It will be seen that the 

 pressure in the heart rises suddenly with the beginning of the ven- 

 tricular contraction and a certain time elapses before this pressure 

 is strong enough to open the semilunar valves. The moment that 

 this occurs (1, on the ventricular curve in Fig. 212) is determined 



