THE ACTIVE FORCES OF LIVING ORGANISMS 25 



evidently the effect and not the cause of this sinu- 

 osity, which can be best explained by supposing a 

 naturally sluggish flow and certain conditions of 

 physical resistance to have existed in the course of 

 development. Moreover, the brain of all the viscera 

 is that which undergoes least massage through bodily 

 movements, and the absence of this stimulus may 

 be looked on as one of the causes of the restricted 

 character of oxidation in nerve centres. In all meta- 

 bolism there are two principal factors, one of which 

 is the blood-supply and its state of oxidation, whilst 

 the other is movement in the tissue, which is both 

 molecular and atomic. 



The action of certain drugs upon the nerve centres The effect 

 illustrates in a curious manner the delicate nature of drugs on 

 the mechanism, the key to which is oxidation in a tkm*^ 

 given. degree. The primary effect of a moderate dose ^'^° °^' 

 of alcohol is to quicken the heart's action, to increase 

 indirectly the contractility of the muscles, and to 



* It will be borne in mind that the effect of a drug on the 

 substance of nerve-cells, or on protoplasm in general, and its 

 effect, especially its primary effect, or its effect in small doses 

 on the organism, are often really opposed to one another. 

 Drugs which diminish oxidation in protoplasm, considered per 

 se by constricting it, cause at first an increase of contractility 

 in the heart and vascular system, and hence indirectly, and 

 within certain limits, produce an augmentation of oxidation. 

 At the same time, the ultimate effect of such drugs — that is to 

 say, the reaction of the system — after they have ceased to act, is 

 in general opposed not to the indirect effect they produce, but 

 to the direct effect on protoplasm. It is for that reason that, 

 in the remarks which follow, attention has been chiefly directed 

 to the latter. 



