336 



PRACTICAL PHYSIOLOGY 



The reservoir is placed so that the level of the fluid in the venous 

 manometer is 3 cm. above the heart, and the clip is then opened. 

 The heart contracts and expels the fluid into the arterial manometer. 

 Note the amount of each systolic output as indicated by the rise of 

 level in this. As the pressure rises the output lessens. Note the com- 

 petency of the auriculo-ventricular and 

 aortic valves, and the elastic swing of 

 the bulbus arteriosus (the dicrotic 

 wave) which follows each systolic out- 

 put. To investigate the competency 

 of the auriculo-ventricular valves the 

 reservoir must be temporarily clipped 

 off from the venous manometer. 



The work of the ventricle can be 

 obtained by multiplying the volume 

 of the output by the height of the 

 lift. The absolute force of the ven- 

 tricle is given by the height of 



FIG. 213. Method of showing the effect of 

 taasion on the apex-preparation. (Pitres.> 



FIG. 214. Method of investigating 

 the action of the valves, the systolic 

 force, output, etc., of the toad's 

 heart. 



the fluid, which the ventricle is just unable to lift. A vigorous 

 toad's heart will lift the fluid up to a height of 1 metre. Let out 

 the fluid in the arterial manometer and lower the fluid in the 

 venous manometer to the level of the heart. The heart will not fill 

 in diastole if the pressure in the latter is not positive. Kaise the 

 pressure in it to 10 and 20 c.m., and observe the effect of the increased 

 diastolic pressure on the systolic output and on the absolute force of 



