446 THE DYNAMICS OF CARDIAC ACTION. 



to that fulfilled by them in all others. Indeed, it is difficult 

 to conceive of a mechanism in which vasoconstriction and the 

 adjustment of functional activity to requirements could be dis- 

 pensed with. These factors, in addition to the normal attri- 

 butes of the afferent fibers of the vagus, i.e., to transmit to the 

 vagal center impulses that will bring about reflexly the required 

 modification of functional activity, constitute a simple, though 

 perfect, mechanism, when applied to the phenomena witnessed. 

 They satisfy equally well the needs of the functional activities 

 of the heart-muscle, when supplemented with the all-important 

 adrenal secretion of the Thebesian circulatory system. 



There are two features of cardiac functions connected with 

 the nervous system, however, which appear to us to require 

 interpretations other than those that have been generally ac- 

 cepted: i.e., the "augmentor," or "accelerator," and the "in- 

 hibitor" phenomena. 



"AlJGMENTOR," OR "ACCELERATOR," PHENOMENA. These 



consist of an increase of the rapidity of the heart-beats and the 

 force of the beat, "the diastole being shortened and the systole 

 strengthened": the type of cardiac action we have termed, when 

 exaggerated as it is in exophthalmic goiter, the "cramped heart." 

 In reviewing another subject Professor Foster says: "If we 

 stimulate the sympathetic in the neck, 17 cutting the nerve below, 

 so as to block all impulses from passing downward, and only 

 allow impulses to pass up to the vagus and thence down the 

 mixed vagus trunk to the heart, we get very remarkable results. 

 The beat of the heart, instead of being inhibited, is augmented; 

 the beats are increased, either in frequency or in force, or most 

 generally both in frequency and in force. The effect is, per- 

 haps, best seen when the heart before stimulation is beating 

 slowly and feebly; upon stimulation of the cervical sympathetic 

 the beats at once improve in vigor and frequency; indeed, a 

 heart which, for one reason or another, has almost ceased to 

 beat may, by proper stimulation of the sympathetic, be called 

 back into vigorous activity." That we are dealing here with 

 stimulation of the adrenals seems probable. 



Indeed, we have added a factor of marked importance to 

 those usually taken into consideration, i.e., the anterior pitui- 



17 All italics are our own. 



