Electromotive Phenom. of the Mammal. Heart. 277 



It was clearly of im].)ortance, theiefoie, to repeat the obseiTations 

 of Waller on the intact animal, and as the capillary electrometer at 

 our disposal at University (college, London was not sufficiently delicate 

 to show so small a variation, by the kindness of Prof. Burdon-Sander- 

 son we were enabled to make use of the apparatus in his laboratory 

 at Oxford. We had also the advantage of Prof. Gotch's assistance in 

 carrying out the observations, and beg him to accept our grateful 

 acknowledgments. 



It is unnecessary to describe in detail the apparatus used, it 

 being essentially similar to that described above. An important advan- 

 tage, however, it had, in that we were able to use the electric arc 

 light in place of the lime-light, and hence greater magnifying power 

 on the projecting microscope. The method of leading off, found to 

 , give the best results, was to place our electrode, consisting of a thick 

 rod of amalgamated zinc having a sponge soaked in brine tied over 

 the end, on the situation of the apex beat; the other electrode consist- 

 ing of a similar zinc rod dipping into a basin of brine in which the 

 right hand was immersed. 



When observed by the eye, the movement of the meniscus ap- 

 peared to consist of two phases, the first short and sharp, and the se- 

 cond more prolonged; the direction of the second was easily made 

 out, but that of the first it was impossible to decide by mere inspec- 

 tion; in fact, different observers had different opinions. A photograph, 

 therefore, was the only possible way. to decide; indeed, when leading 

 off apex beat and epigastrium on one occasion, we thought we obtained 

 a movement showing that the apex became negative first; but a pho- 

 tograph showed that we had completely missed the first phase of base 

 negativity. 



We led off from various parts of the body, but found that apex 

 beat and right hand gave the largest excui^sion, the photograph of 

 wliich in the case of one of us (E. H. S.), is reproduced in Plate XYII, 

 fig. 23 (to be read from right to left); the uppermost of the thi^ee 

 curves is the chi-onograph tracing, marking Yk, sees., the middle 

 one is the tracing of the carotid pulse, obtained by means of a tym- 

 panum, and the lowest one is the movement of the electrometer me- 



