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May 28, 1857. 

 The LORD WROTTESLEY, President, in the Chair. 



The CROONIAN LECTURE was delivered by JAMES PAGET, Esq., 

 F.R.S., " On the Cause of the Rhythmic Motion of the 

 Heart," as follows : 



I have selected for the subject of my lecture, the cause of the 

 rhythmic motion of the heart ; guided to this choice, partly by the 

 belief that the Croonian lecture must have some relation to muscular 

 motion, and partly by the interest which I have acquired in the 

 subject in the course of observations extended, though with many 

 and long interruptions, over some ten or twelve years. 



It is not necessary that I should enter on any consideration of 

 the various opinions that have been entertained on the cause of the 

 heart's peculiar motion. Let me first show what it is, and how it 

 differs from the other motions in the same body, which are visible to 

 the naked eye. 



In a beheaded tortoise, or any other of the Amphibia, the muscles 

 of the trunk and limbs are usually in perfect rest, unless disturbed : 

 those in the head may act so as to produce a kind of gasping and 

 swallowing movements, at distant and nearly regular intervals (an 

 imperfect kind of rhythmic motion) : the digestive and other mucous 

 canals are at rest, or move with slow worm-like actions ; but the heart 

 maintains, with perfect regularity, the rhythmically alternate con- 

 tractions and dilatations of its auricles and ventricle ; its several 

 movements being ordered, not only in the manner of their succes- 

 sion, but in rhythm, i. e. in the proportions of time which they 

 severally occupy. 



Why is this difference ? To what may we refer as the cause of 

 this apparently peculiar mode of muscular movement ? In answer, 

 let me show (for it is a condition of the Croonian foundation that 

 experiments should be shown) that the cause of the rhythmic action 

 is in the heart itself ; not in any of the great nervous centres through 

 which other muscular movements are excited, including those in the 



