94 



known to be readily diminished or cut out altogether by 

 various chemical agencies, etc. 



In many cases of common syncope vagus slowing of the 

 heart down to 50, 40, etc., a minute is a feature, but such 

 slowing is wholly insufficient to account for the fall of blood 

 pressure and the loss of consciousness ; there are other 

 factors concerned. Such cases do not have a fatal issue. 

 Some instances of this condition were described by Lewis'* 

 a few years ago in subjects of " iritable heart." Pretty 

 extensive cardiac slowing is quite compatible with a fairly 

 good blood pressure — vastly higher than what is necessary 

 for the continuance of life. Pronounced slowing (without 

 danger to life as a rule) is, of course, familiar in some forms 

 of violent pain — for example, in biliary and renal colic, etc. 



The conditions under which sudden death most commonly 

 occurs — namely, muscular exertion — are not favourable to 

 prolonged vagus inhibition, but on the contrary are asso- 

 ciated with reduction of the normal vagus control over the 

 heart and concomitant activity of the augmentor nerves, 

 leading to acceleration with increased force of the beats, 

 etc. — conditions favouring the development of fibrillation in 

 predisposed subjects. The same holds good generally in 

 emotional excitement, apart from the very brief standstill 

 (or prolongation of diastole) which may be caused by sudden 

 fright. 



Vagus Inhibition succeeded hy Fibrillation. 



There is another possibility with reference to the effects 

 of vagal inhibition. Experiment has shown that attacks of 

 auricular fibrillation of varying duration sometimes develop 

 after a period of inhibition, sometimes after one or more 

 recommencing auricular beats have occurred. The develop- 

 ment of fibrillation in these instances is definitely related to 

 the occurrence of the preceding phase of inhibition induced 

 by vagus stimulation. 



Fibrillation of the ventricles has also been seen following 

 vagus standstill, but this is a rare phenomenon as compared 

 with the development of auricular fibrillation in similar 

 circumstances. In the course of researches over a great 

 many years I have obtained records of only a very few 

 examples. Still these are enough to indicate that, in 

 presence of undue ventricular susceptibility, fibrillation may 

 sometimes be determined in this way in some of the manifold 

 varieties of abnormal conditions that can occur in man. 

 Thus vagus inhibition, much too brief to be dangerous 

 through the standstill induced, may possibly involve a 

 mortal issue through a succeeding fibrillation. 



Fibrillation or Beflex Inhibition in Sudden Death in 

 Anginal Subjects. 

 The following considerations may be cited in favour of 

 the fibrillation view of death in angina. 

 1. The presence of coronary and myocardial conditions 



