The present study was undertaken to determine possible influences on the cardiac rhythm of heating remnants of the original sinus venosus tissue in the right auricle and neighboring parts other than the sinoauricular node. We have attempted in this work to control accurately the temperature, time of application and definite delimitation of the area affected. The work, in part, is also a critical analysis of this method of localization of a primary cardiac pacemaker, in view of the fact that in many previous studies of this character such accurate controls were not observed.
The method of accurate control of the temperature for localizing automatic tissue in the heart has not, so far as we are aware, been emphasized in any previous work. This method has been employed extensively by a number of investigators for localization of the primary pacemaker (MacWilliam,1 Engelmann,2 Adam,3 Ganter and Zahn4); and for determination