LIX.] ENDOCARDIAL PRESSURE. 28 1 



the lever is horizontal, and writes freely on a slow-moving recording 

 drum. Every time the heart contracts it raises the lever, and during 

 diastole the lever falls (fig. 203). 



In this way it is possible to use various fluids for perfusion. The 

 fluids may be placed in separate reservoirs, each communicating 

 with the inlet tube, and 

 capable of being shut off or 

 opened by clamps as re- 

 quired. Further, by poison- 

 ing the supply fluid with 

 atropine, muscarine, sparte- 

 ine, or other drug, one can 

 readily ascertain the effect 

 of these drugs on the heart, 

 or the antagonism of one 



1 , Fro. 203. -Tracing obtained from a Frog's Heart, 



drug to another. through which Dilute Blood was perfused. The 



Instead of a glass funnel contracting heart raised a registering lever. 



_ & The lower line indicates seconds. 



as a reservoir for the fluid, 



one may use a Marriotte's flask (fig. 204), the advantage being that 

 the pressure of the fluid in the inflow tube is constant. Another 

 simple arrangement is to have a bird's water-bottle, with a curved 

 tube leading from it to the inflow tube of the cannula. 



3. Piston-Recorder (of Schafer). 



The heart is tied to a two-way cannula as before, and is intro- 

 duced into a horizontal tube with a dilatation on it. The tube of 

 the recorder is filled with oil, and as the heart dilates it forces the 

 oil along the tube and moves a light piston resting on it. When 

 systole takes place, the oil recedes, and with it the piston. The 

 piston records on a slow-moving drum placed horizontally and 

 gives excellent results. 



LESSON LTX. 



ENDOCARDIAL PRESSURE APEX PREPARATION 

 TONOMETER. 



1. Endocardial Pressure in the Heart of a Frog. 



(a.) Proceed as in the previous experiment (a.}, (b.) (omit c.), (d.). 



(b.) Arrange a frog's mercury manometer provided with a Avriting-style as 

 in fig. 204. Attach the inlet tube of the cannula to the Marriotte's flasks 

 (a, b), and connect the outflow with the tube of the mercury manometer. It 

 is well to have a f-tube between the heart and the manometer, but in the 

 heart apparatus, as shown and used, the exit tube is preferable. See that 



