INHIBITION AND CARDIAC VAGUS 107 



rapidity and the waste of unregulated energy, power is 

 conserved. Quite legitimately we may regard stroke as 

 the pace-maker, and cox as central control. If in the heart 

 we regard " inhibition " by the vagus as inhibition of 

 the accelerators themselves, we obtain a physiological view 

 of the whole cardiac drama, which, in fact, puts it into 

 line with the muscular phenomena of reciprocal innerva- 

 tion. I am aware that physiologists, dominated by what 

 they observe in the laboratory, maintain that such an 

 illustration does not illustrate, as they say the heart's force 

 is really weakened. But the objections to this are many 

 more than those already mentioned. All the facts of 

 mechanics and physics are against it. When an engine is 

 stopped or slowed, it is not weakened. On the contrary, 

 it is strengthened, i.e. energy accumulates, and the boiler 

 pressure rises. Questions of energetics also arise, for if, 

 as physiologists say, the nerve only pulls the trigger, 

 what action occurs in the heart muscle as it slows ? Does 

 it waste its energy under normal stimulation, postural, 

 inspiratory, or expiratory ? And if its energy is wasted, 

 what becomes of it, and how does its free energy become 

 bound energy ? It seems, having got so far, that no effort 

 has been made to ascertain whether the real function of 

 the vagus, as regards the brain itself, is not to control the 

 accelerator centre, and the action of the accelerator centre 

 to modify vagus action. Such an opinion might, I think, 

 correlate and explain many of the observed phenomena, 

 and it would certainly bring them into line with those seen 

 in engines of all kinds, while it does not contradict direct 

 cardiac action. 



It still remains, even if these views are allowed to have 

 any force, to ask in what way the vagus actually influences 

 the heart ? If it slows it, not to weaken it, but to allow it 



