INHIBITION AND CARDIAC VAGUS 121 



shadow, of certain doctrines, are naturally apt to find on 

 every hand confirmation of the accepted. This is not so 

 only in theology. It is a common human weakness. The 

 justification of criticism lies in the acknowledged con- 

 fusion of the subject, due, almost certainly, to inadequate 

 definitions and the confounding of several subjects under 

 a heading of the very dimmest connotation. It seems that 

 we cannot use the word rightfully even as a temporary 

 " explanation " of vagal action, although we may employ 

 it properly in the interruption of conditioned reflexes where 

 we get cases of substituted action which are as clearly 

 seen on examination as the surprising physical results 

 of apomorphine on a hystoidal patient. To believe that 

 stimulation, or excitation of a nerve, dissipates energy, for 

 that is what weakening means, is impossible. It has been 

 said that the process is no more than the interruption of 

 the storing of energy. How this can occur physiologically 

 is hard to see. It is a mere assumption, and in any case 

 it would not be " weakening." Regulation is not done by 

 enfeeblement in any class of organism except in patho- 

 logical states. That the heart is always being regulated 

 even in easy unstressed conditions is obvious. But I have 

 discovered that it is more regulated than is generally 

 known. Judging from cardiograms of all known kinds it 

 would be said that healthy heart-beats were of equal force. 

 This may be so practically, but it is not so actually. By 

 means of a liquid column in a small tube, actuated directly 

 from the radial artery, and thrown upon a screen with a 

 magnification of the moving liquid until it is, say, ten feet 

 long, it can be seen that few successive beats are equal, and 

 that the dicrotic notch, whether great or small, is perpetu- 

 ally varying. All muscle fibres do not do equal work at 

 all times. Interdependence and regulation are the ruling 



