108 OF VITAL MOTION. 



dilatation, and hence it seems necessary to suppose 

 that there must be something more than mere 

 relaxation in the diastole. 



Another argument in favour of the same conclusion 

 may be found in a case of cardiac-hernia, recorded by 

 Dr. Cruvelhier, in which it is stated that the hand 

 which grasped the protruded heart was opened during 

 the ventricular diastole, notwithstanding a considerable 

 effort to the contrary on the part of the experimenter, 

 a fact which is altogether at variance with the idea 

 that this state is one of mere relaxation. 



These considerations are sufficient to prepare us to 

 expect that the movements of the heart form no 

 exception to other vital movements, and to make us 

 doubt that the ventricular diastole is a condition of 

 relaxation, marking fatigue or weariness after an act 

 of mysterious and exhausting contraction. What, 

 however, is the true nature of this state, and of the 

 systole, will appear if we proceed to examine the 

 heart in relation to its causes of action. 



1. Of extra-organic force as the agent in the 

 movements of the heart. 



The effects of the agents which belong to this class 

 are somewhat obscure, but they are most apparent in 

 the rudimentary phases of life. Low in the scale of 

 creation, in " exsanguine animals, such as the snail," 

 we learn, on the authority of the great Harvey, that 



