PULSE RECORDS IN THEIR RELATION TO THE 

 EVENTS OF THE HUMAN CARDIAC CYCLE 



. BY THOMAS LEWIS 



THE study of the arterial pulse in man has occupied the attention 

 of physiologists and physicians for centuries. With the advent 

 of the graphic method, it yielded, at the hands of such investi- 

 gators as Marey ( 33a ), Landois ( 31 ), Mosso ( 38 ), and a host of other 

 workers, results which have greatly enhanced our knowledge of 

 the human cardiovascular system. Not infrequently it has served 

 to stimulate research on problems of general and far-reaching 

 physiological significance, and in some instances has contributed 

 facts to our knowledge of the heart and arteries which it would 

 have been difficult to obtain from experiments on the lower 

 animals. The study of the human pulse carries with it a natural 

 advantage, which can hardly be overestimated ; the subject of 

 experiment may be observed under normal conditions, and is 

 amenable to reason and more perfect control. 



The examination of the individual curves of arterial sphygmo- 

 grams, upon which an incalculable amount of labour has been 

 expended, is, with the exception of a few instances, abortive in 

 yielding such information to the clinician as can bring him a pro- 

 fitable return for the time he expends. Empirical diagnosis from 

 pulse tracings is a method fraught with abundant and dangerous 

 pitfalls. It is for the evidence which the curves give of the events 

 of the cardiac cycle that they are to be chiefly valued, and it is 

 in this direction that the researches of modern, nay recent, years 

 have yielded such fruitful results. Above all, graphic curves taken 

 simultaneously from different pulsating points are invaluable, for 

 they accord information of the time relations and nature of the con- 

 traction of the separate chambers of the heart. The observations of 

 the past ten years, while. supplying important physiological know- 



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