212 Mr. \V. M. Bayliss and Dr. E. H. Starling. [Nov. 26, 



The character and direction of this variation, however, is exceed- 

 ingly sensitive to slight changes in the temperature of the various 

 parts of the heart, so that in order to obtain a constant result in 

 animals with opened chest it is necessary to use warmed air for 

 artificial respiration. 



The following experiment illustrates the sensitiveness of the direc- 

 tion of t-he electrical variation to changes in the temperature of the 

 respired air : 



June 27, 1890. Dog: Operation as already described; artificial 

 respiration with warmed air. Base of right ventricle (anterior 

 surface) to acid, apex of left ventricle to capillary. 



Direction of variation 



(a.) Before opening pericardium : diphasic base, apex. 

 (&.) After opening pericardium : diphasic base, apex. 



The hot water was now poured out of the vessel surrounding the 

 spiral, and this was filled with ice. After five minutes another 

 photograph was taken of the variation 

 (c.) Triphasic base, apex, base. 



(d.) (After another five minutes.) Diphasic apex base, 

 (e.) The ice was now replaced by hot water. 



After ten minutes more, the variation was found to be once again 

 diphasic, the base becoming negative first. 



Cold air was then used again, with the same result as before. 



The same reversal of the variation can be obtained in the tortoise's 

 heart by warming the apex and cooling the base simultaneously. 



If we may regard the electrometer tracings as reliable, that is to 

 say, if the variation apex, base with cooled base is the real varia- 

 tion, and it is not really a triphasic one with a first phase too small 

 to be read on an electrometer, the only conclusion we can draw from 

 our experiments is that the excitatory wave in the ventricle is a 

 different thing from the wave of negativity, and precedes it (since in 

 the hearts with cooled base, although the ventricles were beating in 

 normal sequence to the auricles, the negativity began at the apex 

 before the base). 



Possibly, in the ventricles, the excitatory state is not transmitted 

 directly from one muscle cell to another, but by the intervention of 

 the intermuscular network of nerves shown by Dogiel, Openchowski, 

 and others, to be universally present in the ventricular walls. 



Time Measurements. Some point of the auricles or ventricles was 

 stimulated three times a second by means of an induction shock. In 

 this way an artificial rhythm is induced, the heart contracting to 

 every stimulation. This is the only method by which it is possible 

 to get time measurements in the mammalian heart, since we cannot 

 put this organ into a prolonged standstill, as we can the frog's heart 

 by means of the Stannius ligature. 



