120 OF VITAL MOTION. 



coronary arteries: and this abundant supply of the 

 vivifying stream cannot be without its influence upon 

 the walls of the heart. We cannot suppose it to 

 excite the systole, however, for the rush is absolutely 

 simultaneous with the opposite condition, namely, 

 with the swelling out of the heart into the diastole. 

 Moreover, there is a short pause before the super- 

 vention of the systole. The blood, in fact, rushes into 

 the walls of the heart at the instant when the diastole 

 commences, remains during the continuance of this 

 state, and throughout the short pause which super- 

 venes, and hence the flood of new blood can scarcely 

 be supposed to be the cause of the systole. There is 

 no difficulty, however, in believing that it is one of 

 the causes of the diastole. The very rushing into 

 the vessels may contribute to this. The reaction, 

 also, which takes place between the oxygen of the 

 blood and the vascular coats, which we know to be 

 one main cause of the capillary force, will co-operate 

 with the arterial tension in producing the same 

 result, for a definite extrication of force is the direct 

 consequence of this reaction. When, therefore, we 

 consider the rush of blood in the coronary arteries, 

 and the attendant actions in the capillaries, we may 

 easily understand that the pulse of blood in the 

 vessels of the heart may be an important coagent 

 with the pulse of nervous influence which takes place 

 at the same time, in bringing about the diastole. But 



