1. The Frequency of Paroxysms of Auricular Fibrillation. —The widespread use of instruments of precision in the diagnosis of cardiac arrhythmias during the past few years, and the resulting improvement in diagnosis, have demonstrated that paroxysmal auricular fibrillation is by no means a rare clinical condition. That it is encountered in a certain variable proportion of hospital patients has been pointed out by a number of observers, most of whom have expressed their belief that the condition occurred more commonly than was recognized, but the highest percentage of cases yet recorded is that of Levine,1 who found that 14.1 per cent. of his group of patients with auricular fibrillation had shown at some time the transient form. This author includes in his series four patients who showed auricular fibrillation only during the transitional stage between auricular flutter and normal rhythm; if these be excluded, his percentage becomes 10.9, which still