THE CIRCULATION OF THE BLOOD. 



273 



a 



tambour consists of a metallic frame covered by a thin rub- 

 ber membrane. By means of flexible tubes, a. v., the in- a 

 terior of each tambour can be placed in communication 

 with the interior of a second tambour provided with a re- 

 cording lever. Pressure applied to the cardiac tambour will 

 be followed by a movement of the enclosed air toward the 

 recording tambour indicated by an outward movement of 

 its membrane and a rise of the lever; removal of the pres- 

 sure will be followed by a movement of the enclosed air 

 toward the cardiac tambour indicated by an inward move- 

 ment of the membrane and a fall of the lever. 



When the tambours are introduced into, and carefully 

 adjusted to the interior of the right heart, the auricular and 

 ventricular contractions will exert pressure on their enclosed 

 tambours as indicated by the rise of the levers of the re- 

 cording tambours, which continues so long as the pressure 

 lasts. With the relaxation of the auricular and ventricular 

 walls the pressure is removed and the levers fall to their 

 former position. When 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. 125. 



A similar record would be obtained if the tambours were 

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



In this record the upper and lower lines rep- 

 resent respectively the contraction and relaxa- 

 tion of the auricle and ventricle as well as the 

 variations of pressure occurring within them. 

 A study of this record shows 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 accumu- 

 lation of blood within the heart cavities. When 

 this reaches a certain level the auricular con- 

 traction 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 within the auricle undergoes variations both in 

 the way of increase and decrease as shown by small undulations on the curve. 



m 



FIG. 124. CARDIAC SOUNDS. 

 v, Tambours to be inserted into 

 the ventricle; a, tambour to be in- 

 serted into the auricle; m, rubber 

 membrane surrounding metal 

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

 connection with tambours. 



FIG. 125. TRACINGS OF (i) THE INTRA-AURICULAR PRESSURE; AND (2) THE INTRA-VENTRICULAE 

 PRESSURE OF THE HORSE. (Chauveau and Marey.) 



With the close of the auricular systole, the ventricular systole occurs 

 quickly and energetically and endures for some time, after which the ventricu- 



18 



