560 CIRCULATION OF BLOOD AND LYMPH. 



stimulation. Fibrillation of the auricles also occurs frequently 

 under experimental conditions, and, indeed, in the human heart ap- 

 parently under pathological conditions. When the auricles are 

 thrown into fibrillation by experimental means the ventricles con- 

 tinue to beat, but in an irregular manner similar to a condition 

 sometimes observed in man and described usually under the term 

 pulsus irregularis perpetuus. There is reason to believe that this 

 condition in man is attributable to a fibrillation of the auricles, t 

 The cause of the sudden change from co-ordinated to fibrillary con- 

 tractions has never been satisfactorily explained. It has been 

 suggested, on the one hand, that it is due to some alteration in the 

 normal process of conduction, the interposition of partial or com- 

 plete blocks in the course of the excitation wave, and, on the other, 

 that it is caused by the independent formation of impulses in 

 many foci throughout the cardiac musculature. 



*Cushny, "American Journal of the Medical Sciences," June, 1911. 



