OF VITAL MOTION. 115 



tole of the auricle is related in point of time to the 

 diastole of the ventricle. But a careful examination 

 of the question is sufficient to disarm this difficulty. 



It cannot be doubted that the auricles, as well as 

 the ventricles, possess a proper power of contracting 

 and dilating, but it is a fallacy to suppose that these 

 states at least in the rapid rhythmic order in which 

 they occur are distinct in themselves, and altogether 

 independent of the movements which have taken place 

 in the ventricles. There is good reason, indeed, to 

 doubt the actuality of auricular-systole as a state of 

 positive and independent contraction, and to suppose 

 it to be, as it were, a pseudo-systole^ consequent upon 

 the sudden emptying of the auricle by the rapid dia- 

 stole of the muscular ventricle. And to this opinion 

 we are led by the anatomical peculiarities of the coats 

 and cavities of the auricles. In the cavities^ the 

 absence of valves to prevent a reflux of blood into 

 the veins, and the want of all evidence of any such 

 reflux (except in patency of the auriculo- ventricular 

 valves, where, indeed, the cavities of the auricles and 

 ventricles are continuous), afford a strong argument 

 against there being any true systole in the auricles. 

 The history of these cavities also, as gathered from 

 the records of comparative anatomy, tends to show 

 that they are mere cisterns calculated to hold the 

 blood necessary to the wants of the ventricles, rather 

 than organs destined to aid in the circulation by systolic 



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