Faradic stimulation of the auricles of animals may produce any one or any combination of the following closely related conditions : 1. Fine Fibrillation. —This may be produced by auricular stimulation alone, but it is favored by simultaneous stimulation of the right vagus nerve.1During fine fibrillation the auricles appear dilated and motionless and from the mechanical point of view they may be said to be paralyzed. Close inspection, however, shows that they are the seat of numerous incoordinated contractions involving very small muscle bundles. It seems certain that this fine type of fibrillation produces no auricular venous waves of any magnitude.2On the other hand, changes in the electrical potential of different portions of the auricular musculature may cause distinct movements of the galvanometer string. The ventricles, being stimulated irregularly, take on a disorderly rhythm. 2. Coarse Fibrillation. —No sharp line separates this from the pre