286 TEXT-BOOK OF PHYSIOLOGY 



1. The period of rising tension, from the beginning of the systole and the 



closure of the auriculo-ventricular valves to the opening of the semi- 

 lunar valves, the pre-sphygmic period, occupying from 0.02 to 0.04 

 second. 



2. The period of ejection, the sphygmic-period, from the opening of the 



semilunar valves to the end of the systole, occupying about 0.2 second. 

 The ventricular diastole may also be divided into two periods: 



1. The period of falling tension or relaxation, the post-sphygmic period, 



from the end of the systole and the closure of the semilunar valves to 

 the opening of the auriculo-ventricular valves, occupying about 0.05 

 second. 



2. The period of filling, from the opening of the auriculo-ventricular valves 



to the beginning of the succeeding auricular systole. 

 The Time Relations of the Successive Periods of the Ventricular 

 Activity of the Human Heart. The duration of each of the periods of 

 ventricular activity as stated in the foregoing paragraph holds true only for 

 the animal the subject of the experiment. The time relations of each period 

 vary somewhat with the animal as well as with the rate of the heart during 

 the time of the experiment. In human beings the same holds true. As the 

 outcome of different methods of investigation the average duration of each 

 period has been approximately estimated as follows : 



Period. Rate 70. Rate So. 



1. Presphygmic o .055 \ Systole o .051 1 Systole 



2. Sphygmic 0.268/0.323 0.254/0.305 



3. Post-sphygmic 0.050 1 Diastole 0.050 1 Diastole 



4. Pause 0.490/0.540 0.395/0.445 



Total Duration 0.863 0.750 



The Intra-auricular Pressure. During the auricular systole the 

 pressure within the auricle undergoes variations as shown by direct examina- 

 tion by means of a cannula inserted into the auricular cavity and connected 

 externally with a recording tambour, or by indirect examination by means 

 of an exploratory tambour placed over the right jugular vein in close relation 

 to the clavicle. The pressure variations in the jugular vein which are thus 

 recorded by means of a tambour provided with a writing lever are believed 

 to be caused by, closely follow and reproduce the pressure variations in the 

 auricle. 



Among the most important of the direct examinations of the auricular 

 pressure are those of Porter, carried out by the insertion of a large cannula in 

 the auricular appendix, or in a pulmonary vein close to the auricle and con- 

 nected by its free extremity with a Hiirthle tambour. The curve of pressure 

 thus obtained, shown in Fig. 126,* is characterized by three positive and three 

 negative waves. Among the more important of the indirect determinations 

 of the auricular pressure variations are those of Bachmann, carried out with 

 highly sensitive recording tambours. The curve of pressure variations in 

 the jugular vein thus obtained, by Bachmann, Fig. 127, is placed in juxta- 

 position for purposes of comparison. 



The first positive wave, a, is caused by the systole of the auricle and 

 amounts to about 9 millimeters of mercury. The first negative wave is due 

 to the relaxation of the auricle. 



