CHAPTER IV 



Inhibition and the Cardiac Vagus 1 



THE history of science records the birth, life, and 

 death of many conceptions, which, although they 

 seemed to reconcile contradictions triumphantly, in the 

 end did but serve to show how hypotheses can rise to the 

 rank of theories, and yet finally be disposed of by some stray 

 fact. Just as some conqueror in his hour of victory falls 

 to a chance bullet, so they succumb at last. They may for 

 the time be " true " ; they serve, that is, as a temporary 

 shelter or clearing house for contradictory observations, 

 and thus produce the semblance of order. Deep within 

 them there may be even some hint of real explanation. 

 It was so with the ancient view of the arteries, to which the 

 very word bears witness. They were, indeed, air vessels 

 even if the observations leading to such a conclusion were 



1 An abstract of this paper was printed in The British Medical Journal, 

 September 14, 1918, and since re-writing and developing it, I note that 

 R. M. M'Nair Wilson (" Meaning of Tachycardia," ibid., January 17, 

 1920) practically adopts Luciani's view, with which I was not acquainted, 

 that the vagus is " a nerve of diastole," and adds, " this nerve would 

 seem not to be inhibitor in the narrow sense, but rather to act by in- 

 creasing the filling time in response, no doubt, to stimulation from the 

 cortex." Although I do not wholly agree with this in all its implications, 

 yet as I have expressed doubts as to whether tachycardia is to be attri- 

 buted to disturbance of the pace-maker itself, it is of interest to me to 

 note that Wilson holds the view that it is due to a compensating accelera- 

 tion when the ventricular systole cannot get rid of the diastolic intake. 

 This, I imagine, is also the opinion of T. Lewis, who states that tachycardia 

 does not originate in the pace-maker. 



93 



