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TEXT-BOOK OF PHYSIOLOGY 



removed and the levers fall to their former position. When 



a. V a\\ nv the levers are applied to the surface of a recording cylinder 



a record of auricular and ventricular contractions is obtained 

 such as that shown in Fig. 120. 



A similar record would be obtained if the tambours were 

 placed in the cavities of the left side of the heart. 



In the graphic record, Fig. 120 obtained 

 by the foregoing method, it is apparent that 

 during the period of repose there is a gradual 

 ascent of the tips of the recording levers, the 

 result of a gradual increase of pressure due to 

 the accumulation of blood within the heart 

 cavities. When this reaches a certain level the 

 auricular contraction occurs rather suddenly, 

 followed by an equally sudden relaxation, after 

 which the auricular walls remain at rest for a 

 relatively long period, though the pressure with- 

 in the auricle undergoes variations both in 

 m a the way of increase and decrease as shown by 



small undulations on the curve. 



With the close of the auricular systole, the 

 ventricular systole occurs quickly and energet- 

 ically and endures for some time, after which 

 the ventricular walls quickly relax and remain 

 at rest until the close of the next auricular con- 

 traction. The summit of the ventricular trac- 

 i n g generally spoken of as the plateau presents 

 a series of elevations and depressions as stated 



metal in a foregoing paragraph. 



A com p ar i son o f the two traces shows that 

 . : f . . . . , 1,11 



between the close of the auricular and the be- 

 ginning of the ventricular systole there is a slight 

 pause known as the inter systolic pause (Chauveau) . The tracings also show 

 that between the close of the ventricular contraction and the beginning of 



FIG. 119. CARDIAC SOUNDS, 

 Tambours to be inserted into 



membrane surrounding 

 frame-work; a, v, ends of tubes in 

 connection with tambours. 



(Marey.) 



FIG. 120. A GRAPHIC RECORD OF (i) THE INTRA-AURICULAR PRESSURE; AND (2) THE INTRA- 

 VENTRICULAR PRESSURE OF THE HORSE. (Chauveau and Marey.) 



the succeeding auricular contraction there is a period during which the 

 whole heart is at rest and during which the cavities are filling with blood. 



