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Capillary Electrometer Records of the Electrical Changes during 

 the Natural Beat of the Frog's Heart. (Preliminary 

 Communication. ) 



By Francis Gotch, M.A., D.Sc, F.E.S. 



(Eeceived March 5,— Bead March 14, 1907.) 



It was shown, in 1880, by Burdon-Sanderson and Page, that when the 

 ventricle of the excised frog's heart is connected with a capillary electrometer 

 by two contacts, one lying on the base and the other on the apex, then every 

 contraction of the heart was associated with electromotive changes of the 

 following type. The electrometer meniscus was displaced in a given direc- 

 tion, the displacement then suddenly returned and, after a certain time, a 

 second final displacement occurred in the opposite direction, which returned 

 slowly ; the recorded displacements are therefore of the type shown in fig. 1 

 of the annexed diagram. Most of these earlier experiments were carried out 

 on the excised heart rendered motionless by a suitable ligature around the 

 sino-auricular junction, and excited to activity by an induced current which was 

 applied to the tissue, near one of the electrometer contacts. The observed effects 

 were demonstrated to be due to the algebraic sum of an active process under one 

 contact, of the propagation of this process to the tissue under the other contact, 

 and of the occurrence of a similar active process at this further point. The 

 two phases, such as occur in fig. 1, were further shown to be indicative of the 

 time relations of these active processes. The electromotive change during the 

 active process causes this tissue to become relatively negative as compared 

 with the inactive tissue. This negativity commences under the proximal 

 contact, nearest to the seat of excitation ; its development is, however, cut 

 short by a similar change occurring under the distal contact situated further 

 off from the seat of excitation, thus giving the first electrometer displacement 

 the character of a single spike. Whilst both changes are in full progress 

 there is no electrical difference between the contacts, and thus an iso-electrical 

 interval occurs ; finally, the change at the proximal contact, having commenced 

 first, ends first, and the distal change outlasting the proximal one, a terminal 

 displacement of opposite sign is produced. All these well-known results have 

 been supposed, with little experimental warrant, to occur in the beating 

 frog's heart in situ, and a discrepancy thus exists between the assumed 

 electromotive phenomena of the beating frog's heart and the electrical changes 

 actually observed in the beating heart of mammals and of man. Numerous 

 records have been obtained in man and mammals by making use of Waller's 



