92 THE ACTIVE FORCES OF LIVING ORGANISMS 



can you obtain this result by any combination of 

 drugs of opposite tendencies, for they must one and 

 all modify the environment of the nerve-cells, and 

 thus alter the character of their rhythm, acting on 

 them simultaneously, and not, as would be necessary 

 if they were to promote general vaso-motor activity, 

 alternately. By means of a cold bath with a certain 

 amount of reaction it is possible to bring about both 

 contraction and expansion, although it is difficult to 

 regulate the degree of each. By means of rapid 

 changes from a warm to a cooler bath, and vice versd, 

 one can stimulate both vaso-motor action and meta- 

 bolism. The influence of such baths, however, is very 

 powerful, and although under certain conditions it 

 may be highly beneficial, yet at the same time it may 

 also be the reverse. If by this means metabolism is 

 set going very rapidly, it is absolutely essential to 

 control the general tendency of it — to keep it, that is 

 to say, with the balance slightly on the side of con- 

 traction and anabolism. One cannot put the matter 

 more truly than by comparing the process to the 

 riding of a bicycle. The short movements of the 

 handle-bar to this side or that enable you to travel 

 quickly and smoothly, but unless you pursue a given 

 direction you will run into the wall or the gutter. 

 That it is very difiticult to maintain a predominance 

 of contraction over expansion in the arterial system 

 when it has become thoroughly relaxed is true, but 

 at the same time it is equally certain that in this way 

 only, and by keeping up vaso-motor mobility, it is 



