Normal Physiological Function. 30 £ 
stopped from the absence of potassium. Later, ionium was added to the 
list, and also lanthanum and cerium, which, owing to contamination with 
actinium, appeared to possess a trace of radio-activity. The gaseous emana- 
tion (Ramsay's niton) which escapes from radium when it is kept in aqueous 
solution was also investigated. This element, which emits a-particles, was 
also found to restore pulsation to a heart which has been brought to 
a standstill through absence of potassium. Attempts were made to replace 
potassium by some non-radio-active element, but all atterppts were 
a failure except in the case of caesium, to which, however, radio-activity has 
been repeatedly ascribed.* 
These results were sufficiently striking, but the question naturally 
arose as to how far the disintegrating atom was concerned in the process ; 
i. e. whether the corpuscular radiation alone could excite or restore the 
heart’s function. This question was answered in the affirmative by the still 
more striking experiment of bringing a glass bulb, containing mesotborium 
giving off /3-rays, near a heart which had been rendered motionless by 
perfusion with potassium-free Ringer’s fluid. The pulsation was found to 
return invariably, sometimes in as short a time as three minutes. It was 
also proved later that the a-radiation from polonium was in some cases 
competent to restore pulsation to a heart. 
It will be noticed that the potassium emits /3-radiation (negative), while 
the heavy elements which can replace it emit to a large extent a-radiation 
(positive). The heart can thus be stimulated equally well by substances 
emitting either the negative or the positive rays. It was also observed 
that when substances emitting both a- and /3-radiation are supplied to the 
heart together, they have an antagonistic action, and in appropriate con- 
centrations can be made to neutralize one another. 
The capacity of the heavy radio-elements to replace potassium and 
the corresponding antagonism has also been observed recently by other 
workers in connexion with the retention of sugar by the kidney and in 
a certain number of other physiological processes. 
The mode of action of these corpuscular radiations is not clear. The 
charged particles as they shoot along will act by induction, detaching every- 
where electrons from their atoms ; they also transfer kinetic energy, and 
when they come to rest, on, say, some colloidal complex of the cell, they 
will transfer their electric charge and so may set free some ion absorbed on 
the surface. 1 2 Whatever the nature of the action, Zwaardemaker concludes 
that ‘ radio-activity is a mighty biological factor capable of restoring a lost 
function ’. 
1 It is possible that we have in the frog’s heart a physiological test of radio-activity even more 
sensitive than the physical methods at present available. 
2 The radiation of the fixed potassium of the heart muscle appears to be inactive ; the reason 
for this is not clear. 
