86 THE ACTIVE FORCES OF LIVING ORGANISMS 



directly affected, then it is natural to assume that the 

 nerve-cells with which they are connected are in- 

 fluenced in a similar manner, that the rhythm of 

 their metabolism is suddenly altered, and that the 

 molecules of which their protoplasm is composed, 

 though still continuing to vibrate, are grouped in 

 closer order. Indeed, if cold, like heat, be, as it is 

 generally held to be, a distinct form of active force — 

 and this view receives support from the phenomenon 

 of freezing — it is but natural that it should act 

 upon the nervous system dynamically ; and if this be 

 allowed it is difficult to conceive any other way in 

 which it can act than that just suggested. If the 

 arterial blood-pressure be normal, the contraction 

 caused by the sudden application of cold will be 

 accompanied by a diminution of oxidation in the 

 nerve- cells even when allowance is made for anything 

 in the way of added tone to the arterial system, and 

 the expansion caused by heat will be accompanied by 

 a corresponding increase of oxidation when in the 

 same way allowance has been made for the more 

 relaxed state of the arteries. 



A cool or cold bath, when there is no reaction, may 

 be said to produce a general effect of peripheral con- 

 striction and a diminution of oxidation in the nervous 

 system, and thus throughout the body. To obtain 

 this result it is employed in cases of fever. In this 

 way the metabolic rhythm of the nervous system is 

 altered, and it is brought from a state of excessive to 

 one of diminished oxidation, and at the same time 



