112 WARFARE IN THE HUMAN BODY 



it down upon the deck, and placed a coin upon it. The 

 heart continually raised and lowered the piece of money. 

 When it was raised the heart was widely expanded and 

 semi-transparent. As the organ contracted to a mere 

 knot it lost its transparency. But the point is that the 

 detached heart, even in hot, dry air, for very many minutes 

 actually did work. I have been assured that I may have 

 mistaken the systole for the diastole. I do not see how this 

 can be. Ignorant as I was of physiology, I could still 

 observe the time of its greatest expansion when it raised 

 the weight put upon it. In spite of our ignorance of the 

 exact mechanism it seems impossible not to think that there 

 are direct diastolic agents, and that it is they which are 

 governed and regulated by the vagus. It should come 

 into play, especially when the heart is irritable and shows 

 a tendency to rely upon acceleration rather than the 

 "long pulled-through stroke" permitted by an adequate 

 diastolic action. Such action would tend to keep the blood- 

 pressure normal, and increase the coronary blood-supply. 

 It thus becomes easy to understand an efferent cranial 

 nerve acting not as a simple motor nerve, but as part of the 

 autonomic sympathetic system, and it puts vagal cardiac 

 action into line with its positive effects on intestinal move- 

 ments. It is not too much to say that the physiological 

 stimulus affecting the vagus probably depends on an 

 increased irritability in the medulla, consequent on a 

 lessened blood-supply, which reflexly exerts its influence on 

 the vagal centre. The whole drama of the heart, indepen- 

 dently of its automatic action, thus depends for stress and 

 change on the regulating effects of vagus and accelerator. 

 The accelerator, indeed, seems a better term than Gaskell's 

 " augmentor," for its chief role appears to be that of over- 

 coming the inertia of the " pace-maker," and urging the 



