326 Dr. F. Gotch. Records of Electrical Changes [Mar. 5, 



the period from (c) to (d) may be interpreted as the time taken by the 

 propagation of the active state back again from the apex to that part of the 

 base from which the aorta springs, in this instance also at a rate of from 

 130 to 140 mm. in 1 second. 



Control experiments, with a contact upon the aortic bulb, showed that this 

 second reversal was not due to the development of electromotive changes in 

 the aortic wall or bulb, these being too feeble to affect the recording instrument. 

 Moreover, although curves showing double reversals of the type shown in 

 fig. 3 are obtained when the heart begins to get distended with blood, if, by 

 further aortic compression, this distension becomes considerable, then the 

 records tend to return to the type indicated in tig. 1, the ventricle base effect 

 near the aorta being now almost imperceptible ; on removing the distension 

 and letting the blood out of the swollen heart by cutting through the bulb, 

 curves of the type shown in fig. 3, with the double reversal of the first phase, 

 are again obtained. It thus appears that adequate blood supply through 

 intracardiac pressure brings into prominence the activity of that part of the 

 ventricle which leads up to the aorta, and that this favourable influence, 

 although interfered with by considerable distension, continues after the blood 

 has left the heart ; hence the new phenomena of double reversal are not 

 directly caused by intraventricular blood pressure, but are indirectly asso- 

 ciated with a previous adequate blood supply of the muscular tissue forming 

 the ventricular wall. A number of experiments carried out with different 

 positions of contacts and under a variety of conditions (local slight injury, 

 local warming, etc.) have convinced me that the cause of the double reversal 

 is the circumstance that, during the ventricular contraction, a wave of activity 

 starts in that part of the base which is not immediately related to the aortic 

 exit, and that this, having been propagated to the apex, then returns from 

 the apex to the aortic part of the base. 



Only one class of such experiments need be referred to in this preliminary 

 communication. If contacts are placed on each lateral margin of the base 

 near the groove, so that one lies upon the left side remote from the aorta, the 

 other upon the right side near the spring of the aorta, then each natural 

 beat of the heart is associated with electromotive effects of the type shown 

 in fig. 4 ; these become more and more pronounced under the special con- 

 ditions which favour the appearance of the double reversal. The curve given 

 in fig. 4 shows the auricular beat commencing at the point (a) ; this is 

 followed after an interval of 0"*45 by the base effect which begins at the 

 point (b). JSTow, since the rise of the curve indicates relative negativity of the 

 tissue under the contact on the left margin of the groove, which is remote 

 from the aortic exit, it is clear that the change activity must commence here 



