THE HEART 123 



by Gaskell as the * anabolic nerve ' of the heart, and he 

 has compared it to a vaso-dilator. 



The vagus control is in constant action, but varies 

 greatly in different individuals and in the same individual 

 at different times. It keeps the heart slightly ' reined 

 in,' as it were, and conserves its energy, for after a period 

 of increased vagus control the vigour of the heart is 

 augmented. Putting aside the results of physiological 

 experiment, clinical observation* has clearly shown that 

 when the vagus influence is removed the rate and force 

 of the heart-beat are both increased, but the former 

 more notably than the latter. There are limits, how- 

 ever, to the increase of rate observed as the result of 

 vagus lesions in man. In no such case have the heart- 

 beats amounted to more than 160 per minute. Pulse 

 rates above this, therefore, cannot be due to vagus 

 paralysis alone. The increased rate is observed when 

 either vagus is destroyed, but, of course, rather more 

 markedly when the influence of both has been with- 

 drawn. Nor has cardiac dilatation been observed in 

 such circumstances, not even when the lesion has been 

 present for many months. This is to be explained by 

 the independence of the ' tone ' of the heart of nervous 

 influences. 



The influence of the sympathetic nerve upon the 

 heart is exactly opposed to that of the vagus, and is 

 directed to increasing the force and frequency of the 

 beats. For that reason it is spoken of as the accelerator 

 or augmentor nerve. It is probable, however, that these 



* See a collection of twenty-four cases by Martins, 'Tachycardie,' 

 p. 37 (Stuttgart, 1895). 



