oe 
Mr Mines, On Pulsus alternans,. 35 
method—truitful in so many directions—of taking simultaneous 
records of the activity of the heart by two or more instruments. 
In this way it has been found both clinically and in experiments 
on animals, that although in many instances the alternation is 
shown alike in pulse record, cardiogram and electrocardiogram, 
this is by no means invariably the case. Thus it may be well 
marked in the apex beat but absent from the radial pulse (Hering, 
1908) ; it may be present in the electro-cardiogram but in opposite 
phase to the apex beat or to the radial pulse, so that the large 
excursions in the one record correspond to the small excursions in 
the other. There may be similar “incongruence” between apex 
beat and pulse wave and also between two cardiograms taken from 
different points on the same chest wall (Hering). 
The appearance of an extra-systole, whether spontaneous or 
artificially provoked, may profoundly affect the course of an 
alternating series of beats, while progressive changes in such a 
series without intentional or perceptible change in the external 
conditions is frequently noted. The interest of all clinicians has 
been attracted by Mackenzie’s statement that the appearance of 
pulsus alternans in a patient usually means death within two 
years. Such are the facts which have led Lewis (1911) in a 
recent review of the subject to characterise pulsus alternans as 
“one of the most mysterious and most important mechanisms of 
the heart with which clinicians have to deal.” 
The interpretation of pulsus alternans. 
I have already stated that Gaskell in 1882 gave an explanation 
of pulsus alternans. Largely owing to the overwhelming interest 
of his later work on the tortoise heart, the full significance of 
Gaskell’s explanation has been overlooked and another view, 
superficially resembling it and really forming one special case 
of it, has been widely adopted. The recent discoveries about 
pulsus alternans have shown this view to be inadequate. 
I shall first quote Gaskell’s explanation and examine the 
grounds on which its single assumption is founded; I shall then 
discuss the more recent hypothesis which makes the same funda- 
mental assumption, but neglects its logical consequence, and finally 
I shall show how Gaskell’s original suggestion lends itself to the 
interpretation of the various phenomena which at first appear so 
perplexing. 
Gaskell’s experiments on the frog’s heart showed conclusively 
the following facts about alternation : 
(1) that it depended on a local alteration in the condition of 
the ventricle ; 
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