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result is mere oscillation or inco-ordinated quivering of the 

 ventricular wall.?, with complete loss of the expulsive power 

 normally brought to bear on the contained blood by the 

 strong and simultaneous state of mechanical tension present 

 in all the muscular fibres during the normal systole. The 

 effect on the circulation resembles that of absolute stoppage 

 of the ventricular beat with complete cessation of its mus- 

 cular activity, such as may be caused by the introduction of 

 certain poisonous agents", etc. While fibrillation is of 

 universal occurrence, under certain conditions, in all warm- 

 blooded animals — both mammals and birds — its tendency to 

 persist when once established varies greatly, being much 

 greater in the higher mammalian types. In some animals 

 among the lower mammals (rat, rabbit, etc.), as well as in 

 some birds, spontaneous recovery from fibrillation frequently 

 occurs, but in the higher mammals, and probably in man, 

 the condition of true fibrillation seems to be invariably fatal 

 — in the absence of the remedial measure of cardiac 

 " massage," which may, in animals at least, be supple- 

 mented by the administration of certain drugs, while arti- 

 ficial respiration is maintained. Some instances of assumed 

 spontaneous recovery in the higher mammals and in man are 

 probably not cases where true fibrillation had been fully 

 established, but a related though essentially different con- 

 dition, which may easily be mistaken for true fibrillation. 



The essential feature of fibrillation is the establishment of 

 a mechanism of circulating excitation in the musculature, 

 depending on a derangement of the normal relations of 

 (1) the time taken for conduction of the excitation wave 

 over the ventricular muscle, and (2) the refractory period 

 of the individual fibres. If the conduction time is unduly 

 prolonged, or the refractory period is relatively too short, 

 re-excitation is apt to occur when the excitation wave 

 reaches fibres that have already recovered sufficiently after 

 the previous excitation to respond again ; the excitation 

 wave can then circulate through the complexly arranged 

 intercommunicating fasciculi ; after a time it becomes 

 feebler and slower as exhaustion develops, until in a few 

 minutes all visible movement becomes extinguished. If 

 rhythmical compression (massage) of the ventricles is 

 employed (while artificial respiration is kept up) the fibrilla- 

 tion may be maintained for prolonged periods (an hour or 

 longer), with ultimate recovery under favourable conditions ; 

 and such a heart may show regular and vigorous action for 

 the remainder of a long experiment extending over hours. 



So long ago as 1887' I described this mechanism as a peri- 

 staltic contraction wave along the complexly arranged and 

 intercommunicating muscular bundles, in contradistinction 

 to the normal beat. 



" The peristaltic contraction travelling along such a structure as 

 the ventricular wall must reach adjacent muscle bundles at different 

 points of time, and since these bundles are connected with one 

 another by anastomosing branches, the contraction would naturally 

 be propagated from one contracting fibre to another over which the 



