124 WARFARE IN THE HUMAN BODY 



heart is sometimes unexcitable by a direct stimulus when 

 under vagal stimulation is just what would be expected 

 if the vagus is a controller and regulator until it conveys a 

 shock. So to say that the accelerator improves conduction 

 means no more than to say the whole heart is stimulated. 

 It is, again, a mere re-statement of an observation. 

 The truth seems to be that the accepted doctrine of the 

 heart is full of verbal logical fallacies. To declare that 

 " inhibition " causes lessened action is only to say that 

 lessened action occurs because it is somehow not so strong 

 in action as it was. We observe it, but to attribute it to 

 " inhibition " is to repeat the error of the bacteriologists 

 who attribute agglutinations to mystic " agglutinins," and 

 make an observation into a cause. If it is said that by 

 inhibition a cause is not meant, but that the word enables 

 us to link phenomena together, the question at once arises 

 whether they are not falsely linked. We cannot truly 

 oppose it to excitation, which after all is one of the purest 

 examples of a " cause " in physiology, for, whether its 

 nature is understood or not, we can bring an infinite number 

 of legitimate analogies to illustrate it. And, biologically, it 

 is seen that in any organism real inhibition is effected by 

 means of secretions which are very definite agents. Accord- 

 ing to P. F. Herring, feeding rats with thyroid causes not 

 only forced positive changes, such as a three-fold enlarge- 

 ment of the heart, and doubled weight of adrenals, but 

 negative ones such as a smaller thyroid. The gland is 

 not needed, is thrown out of action, and " inhibited " by 

 definite loss of function. No analogies can help out " inhi- 

 bition "if in all cessations or stoppages or weakening of 

 action we find substituted processes of direct action by 

 definite agents. When it is said, as has been said to me, 

 that a pure analogy of true inhibition is when a labourer 



