RHYTHMIC MOVEMENTS. 217 



current of a voltaic pile, and ceases when the 

 current is discontinued." s 



Molecules of one kind are peculiarly arranged 

 in a whorl or vortex (the distinguishing charac- 

 teristic of the heart), producing when in a state 

 of excitation the rhythmic motion. The less 

 complicated and simple spirals are probably modi-- 

 fications of the intricate whorl, producing a less 

 powerful movement. 



It is seen that a portion of the muscular fibres 

 which surround the auriculo-ventricular orifices 

 of the heart are continuous with the segments of 

 the valves, and with the chordce tendenece, and 

 through them with the musculi papillares, the 

 fibres of which belong chiefly to the innermost 

 layer. As these spiral electrodes ascend inter- 

 nally in a direction opposite to that in which 

 they descend externally, " consequent points or 

 secondary poles " 2 are produced, and the electric 

 current transmitted in one direction would cause 

 the contraction of the musculi papillares, thus 

 closing the valves of the heart by making the 

 segments tense ; and, transmitted in the other 

 direction, would allow the valves to remain open. 

 " This rhythmic contraction of the muscles is 

 continually and regularly repeated after short 

 and equal intervals of repose." Annular fibres 

 encircle the auricular appendages of the heart 



1 Guillemin's Forces of Nature, p. 16. 



2 Ibid. Fig. 422, p. 6 1 6. 



