ADVANCED EXPEEIMENTAL PHYSIOLOGY 



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the ventricle. The absolute force is increased by thus raising the 

 diastolic pressure. Too high a filling pressure will throw the heart 

 into diastolic paralysis. The auricle is paralysed much sooner than 

 the ventricle. 



The Isometric Contraction of the Heart (0. Frank's Method). 

 Fine cannulae are placed in the aorta and vena cava inferior and the 

 cannulae are connected with the elastic manometers as in Fig. 215. The 

 taps control the filling and output of the heart. The filling tube a 

 1 c.c. pipette is calibrated in T J<j c.c. The chambers of the 

 manometers are made small and the levers light. The amount of fluid 

 which must enter the manometer during the change of pressure is 

 thereby made as small as possible, and the errors due to inertia are 

 avoided. The outlet tap is opened and the heart is allowed to empty 

 itself. This tap is then closed, and curves of ventricular and auricular 

 systole taken. 



A measured quantity of Ringer's solution is then admitted into the 

 heart through the inlet tap, and new curves taken. This is repeated, 

 and with each increase of diastolic expansion systolic curves are taken. 

 The manometers are calibrated by placing them in connection with a 

 mercurial manometer and a pressure bag or bottle. The following is 

 an example of how the maximal tension is obtained : 



Filling in c.c., O'O 0'09 O22 0-36 048 0'68 



Maximal tension, 12 mm. Hg. 48 66 70 67 64 



FIG. 215. Isometric record of the heart. 



Fia. 216. Effect of increasing dia- 

 stolic pressures on the isometric curve 

 of the frog's heart. (O. Frank.) 



The tension of the heart-muscle obviously increases up to a maximum 

 with the diastolic filling. Beyond a certain point it decreases. The 

 maximal tension of the auricle is obtained by ligaturing the auriculo- 

 ventricular groove. It is ^ to | of the maximal systolic tension. 



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