112 OF VITAL MOTION. 



tions of the heart are very hurried, and when, at the 

 same time, the paleness of the skin shows how small 

 a quantity of blood is forced into the vessels, the only 

 manner in which it is possible to account for the 

 inconsistency of these phenomena, is to suppose that 

 the walls of the ventricles have become contracted, 

 for if these cavities preserved their natural dimensions, 

 the increased number of systolic contractions must 

 produce an equivalent distention of the vessels, by 

 which the skin would become hot and flushed, instead 

 of being, as it is, cold and pallid. And hence it may 

 be presumed, that a state of contraction has been 

 induced under the influence of fear, in the walls of the 

 heart, as in other muscular structures. 



In the natural action of the heart, also, there is 

 strong presumptive evidence that the systole is 

 cotemporaneous with an interruption in the supply of 

 nervous influence, and not with any increased supply. 

 We know, indeed, that the development of this agent 

 is proportionate to the flow of blood to the sources of 

 innervation ; and hence we may conclude that this de- 

 velopment must follow an intermittent law in animals 

 provided with hearts. At the systole, indeed, a gush 

 of blood will pass to the nervous organs and produce 

 signs of activity in them; and as the distribution of 

 force will be consentaneous with its production for 

 in subtlety this agent is analogous to electricity it 

 follows that the heart is most freely supplied with 



