224 EXPERIMENTAL PHYSIOLOGY. 



(/.) Place the heart in a cylindrical glass tube, fixed 

 on a stand, and arranged so that the cork in which the 

 cannula is fixed fits into the mouth of the tube. A short 

 test-tube does perfectly well. The lower end of the glass 

 tube has a small aperture in it through which the thread (c) 

 is passed, and attached to a writing-lever arranged on the 

 same stand as the glass vessel. See that the lever is hori- 

 zontal, and writes freely on a slow-moving recording drum. 

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

 diastole the lever falls. 



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

 The fluids may be placed in separate reservoirs, each communi- 

 cating with the inlet tube, and capable of being shut off or opened 

 by clamps, as required. Further, by poisoning the supply fluid 

 with atropin, muscarin, spartein, or other drug, one can readily 

 ascertain the effect of these drugs on the heart, or the antagonism 

 of one drug to another. 



Instead of a glass funnel as a reservoir for the fluid, one may 

 use a Marriotte's flask (Fig. 104), 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 

 introduced 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. 



LESSON L. 



ENDOCARDIAL PRESSURE APEX 

 PREPARATION. 



1. Endocardia! Pressure in the Heart of a Frog. 



(a.) Proceed as in the previous experiment (a.), (6.), (omit 

 c.), (d.) 



