34 - Mr Mines, On Pulsus alternans. 
On Pulsus alternans. By GreorGE Ratpy Mines, M.A., Fellow 
of Sidney Sussex College, and Additional Demonstrator of Physio- 
logy in the University of Cambridge. (From the Physiological 
Laboratory, Cambridge.) 
[Read 28 October 1912. ] 
[Puate I] 
Introduction. 
THE condition of pulsus alternans, described clinically in the 
first place by Traube in 1872, has long been recognised as due to 
alternation in the strength of the ventricular contractions. Alterna- 
tion in strength of ventricular contractions of the isolated frog’s 
heart was observed, described and explained by Gaskell in 1882. 
After this, for nearly twenty years, the subject received 
but little attention. Within the last ten years a number of 
papers have appeared, dealing both with the clinical and experi- 
mental aspects of the matter. Hering (1902) and Volhard (1905) 
in particular have insisted on the distinction to be drawn between 
true pulsus alternans, in which the ventricular contractions are 
evenly spaced, and pulsus pseudo-alternans or bigeminus pseudo- 
alternans, in which the intervals between the beats, as well as the 
strengths of the beats, show alternation. 
In the latter condition, the variation in size of the ventricular 
contractions depends immediately upon their being provoked when 
the ventricular muscle is in different stages of recovery from its 
last excitation and does not of necessity connote any abnormality 
in the properties of the ventricular muscle. 
In the present paper I am concerned only with the condition 
of true pulsus alternans, that is to say, the condition in which the 
ventricular beats follow regularly-occurring auricular beats at 
perfectly rhythmic intervals*, but in which the musculature 
behaves differently in successive responses, though in the same 
way in alternate responsest. 
The most important additions to our knowledge of this condi- 
tion which have been made in recent years have resulted from the 
* Under these circumstances, the pulse wave corresponding to the weak 
contractions arrives at the wrist a little late, so that the sphygmographic tracing 
shows unequal intervals between 1 and 2, and 2 and 3. Volhard shows that this is 
due to haemodynamic factors. F 
+ For convenience of discussion I shall refer from time to time to a series of 
beats, 1, 2, 3, 4, etc., referring to the beats 1, 3, 5, etc. as the “‘ odd series”’ and to 
the beats 2, 4, 6, etc. as the ‘‘ even series.” 
