INTERPRETATIONS OF THE INITIAL PHASES OF THE 

 ELECTROCARDIOGRAM WITH SPECIAL REFER- 

 ENCE TO THE THEORY OF "LIMITED 

 POTENTIAL DIFFERENCES" * 



SIR THOMAS LEWIS, M.D., F.R.C.P. 



LONDON 



The subject chosen for this lecture is one on which much has been 

 written in recent years, but upon which there is still no complete con- 

 sensus of opinion. In a review x written about three years ago I 

 attempted to explain the constitution of the electrocardiogram on a 

 new basis and put forward views of a novel kind. These views have 

 been accepted by a number of workers ; from other workers they have 

 received criticism, publicly or privately expressed. The lack of uniform 

 conclusions, I think, results largely from misunderstandings, such mis- 

 understandings as may be expected to arise when the subject discussed 

 is not only intricate but concerned with the ultimate processes of 

 cellular activity and its manifestations. In studying the electrocardiogram 

 we attempt to explain its general deflections in rational terms, yet the 

 terms which we are forced to employ are terms which refer to intimate 

 and intangible effects of cellular physics and chemistry. Although, as 

 may be acknowledged at once, I have experienced recurring difficulty in 

 my attempts clearly to conceive the manner in which the electrical 

 events are related to events in the muscle; yet the conception at which 

 I arrived some few years ago and which is now reconsidered in the 

 light of recent discussion and observation has not altered fundamentally, 

 though it may, perhaps, have grown a little clearer during the interval. 

 In attempting a more distinct statement of the case it seems desirable to 

 state that while I refuse to stand committed, once and for all. to these 

 views, yet our present knowledge does seem to necessitate movement 

 from the older hypotheses in some such direction as will be indicated. 



In discussing the question before us one rule stands out as paramount 

 in importance ; the facts and the hypotheses must be divided from each 

 other as scrupulously as possible. Hypothesis cannot be avoided, per- 



* Seventh Mellon lecture. 



* Working on behalf of the British Medical Research Council at University 

 College Hospital Medical School, London. Delivered before the Society for 

 Biological Research, School of Medicine, University of Pittsburgh, May 8, 

 1922. 



1. Lewis: The Mechanism and Graphic Registration of the Heart Beat, 

 London, 1920. 



