HEART 



415 



the left side of the heart, (ix.) Variations in the size of 

 the heart may be recorded by enclosing the ventricles in 

 some form of cardiometer (p. 411). 



(1) It has thus been shown that the adaptation is largely 

 independent of the central nervous system, although this too, 

 as will laier be shown, plays an important part. 



Fig. 179.-— To show the effect of a sudden rise in arterial pressure upon the 

 cardiac contractions recorded by enclosing the heart in a cardiometer. 

 The upstrokes are systolic. Note the increased diastole with the 

 increase in the systole. i^.P., the arterial blood-pressure ; V.P.,the 

 venous blood pressure. (Starling.) 



(2) By such an apparatus it is found that the output of 

 blood is not dependent on the arterial pressure, but that 

 within wide limits of pressure the heart continues to pump 

 out tlie same amount of blood at each systole, thus doing a 

 greater and greater amount of work as the arterial pressure 

 With a sudden rise of pressure it may fail to do so 



rises 



