80 CROONIAN LECTURES 



From our want of knowledge how and where 

 the effects are produced, the greatest possible 

 difference of opinion exists as to the action and 

 work of all the different classes of medicines 

 stimulants, sedatives, tonics, alteratives, spe- 

 cifics, evacuants. 



We are almost led to say that stimulants 

 create force, because they increase contractility 

 and sensibility ; that sedatives destroy force, 

 because they diminish contractility and sensi- 

 bility ; that tonics create force, and specifics 

 destroy force, and alteratives change force. 



But the law of the conservation of energy 

 requires us to believe that no food and no 

 medicine can cause the creation or the de- 

 struction of the slightest particle of energy. 

 The amount of conversion of potential into 

 actual energy may be made more or less, The 

 conversion of one kind of motion into another 

 kind may be diminished or increased, but no 

 annihilation nor creation of force is possible. 



We must cease to regard the so-called im- 

 ponderable heat, or its negation cold ; friction, 

 or its negation rest ; electricity ; light, etc., as 

 entities that can be increased or diminished as 

 remedies ; and we must begin to look at them 



