THE HEART PRETHYSMOGRAPH 



137 



the lateral orifice being closed with rubber tubing and a spring clip. This 

 gives a record by the plethysmographic method ; (ii.) by attaching the tube 

 T to the end, a, of a small mercury manometer, fig. 108, n. On the tube A is a 

 three-way tap, t, which can be turned so that the tube a is connected with the 

 manometer m only, with the exit tube b only, or with both, or completely closed. 

 The movements of the manometer are recorded by a small glass float, F, pro- 

 vided with a glass writing point. This latter method is that of Kronecker's 

 frog-heart manometer. The first method records changes in volume. The 

 second method records the pressure attained by the fiuid with each contraction. 

 As soon as the heart is fixed in position it may commence to beat rhyth- 

 mically, especially if the internal pressure be raised by altering the position 



Fig. 108.- 



-Fro«-heart Plethysmoukaph by which the Pressure Changes 

 can also be recorded by a small manometer. 



of the burette of circulating fluid. If it remain quiescent it may be stimu- 

 lated by sending induced shocks through it by connecting the secondary coil 

 (1) to the wire touching the heart at its base ; and (2) to the stout wire, w. 

 It is not necessary for the upper end of w to touch the heart, it need 

 only be brought near to it. Bring the secondary coil nearer to the primary 

 until the induced current is sufficient to cause a contraction. Repeat the 

 stimuli every three seconds and record the contractions. After a certain 

 time the heart ceases to beat altogether, but before doing so it becomes 

 irregular. A commonly observed form of irregularity is where it gives series 

 of beats arranged in groups. These are termed Luciani's groups 



