174? THE MOTION OF THE BLOOD. 



Dr. Whytt, and all old writers, declare, that, on opening living 

 animals, they saw the auricles (that is, the appendix of the 

 auricles) contract the first ; and this is the modern experience of 

 many. I have seen this in an ass stupified with prussic acid, 

 opened by the desire of Dr. Hope. But in the same ass I re- 

 peatedly saw the appendices of the auricles contract many times 

 to one contraction of the ventricles, resembling the tongue in 

 the act of lapping, and repeatedly saw them contract after the 

 ventricles. Whytt, though in experimenting upon a frog he saw 

 the contraction of the auricle regularly precede that of the ven- 

 tricle, says that the auricle continued to beat long after the 

 ventricle had ceased : in an experiment upon a rabbit by Dr. 

 Stevens, presently to be mentioned, it contracted for nearly three 

 hours, though the ventricle was almost motionless. Sir B. Brodie, 

 in all his experiments on dogs, rabbits, &c. never saw " any regular 

 systole of the auricles corresponding to, and alternating with, 

 that of the ventricles, and often used to observe several slight 

 contractions of the auricle, especially of the appendix of the 

 auricle, for one of the ventricle." 



The contraction of the appendices of the auricles is allowed 

 to be very slight?, and can hardly have much share in the circu- 

 lation. The sinuses are always charged with blood, as reservoirs, 

 and the appendices are probably intended only to enlarge the 

 space by yielding under congestion. The contraction of the 

 appendices is perhaps partly to prevent the blood from coagu- 

 lating in them, as it might do, from their being blind pouches, 

 were it not continually expelled. The sinuses of the auricles 

 must part with some of their blood whenever the ventricles ex- 

 pand ; and this period, the moment after the contraction of the 

 ventricles, is the period at which the systole of the auricles 

 must occur. 



When the ventricles are nearly filled, and still more when con- 

 tracting, the blood must accumulate in the auricles, and the stop- 

 page be felt even in the large veins ; for which reason, just before, 

 or rather at, the moment of the systole of the ventricles, we some- 

 times see the jugulars swells Some have adduced the swelling 

 of the jugulars before the stroke of the heart, as a proof that the 

 auricles contract before the ventricles ; but I have always found 



Dr. Hope's work, p. 37. sq. P Dr. Hope, 1. c. p. 39. 



* See my Lumleyan Lectures on the recent Improvements in the Art of distin- 

 guishing the various Diseases of the Heart, p. 1 6. folio, with copperplates. London, 

 1830. 



