IS THE BODY A MACHINE? 45 



the individual experimented upon makes any mo- 

 tions, there is an accompanying elimination of 

 waste products and a development of heat. But 

 this does not appear to be demonstrable for the 

 actions of the nervous system. Although very 

 careful experiments have been made, it has as yet 

 been found impossible to detect any rise in tem- 

 perature when a nerve impulse is passing through 

 a nerve, nor is there any demonstrable excretion 

 of waste products. This would be a serious objec- 

 tion to the conception of the nerve as a machine 

 were it not for the fact that the nerve is so small 

 that the total sum of its nervous energy must be 

 very slight. The total energy of this minute ma- 

 chine is so slight that it can not be detected by 

 our comparatively rough instruments of measure- 

 ment. 



In short, all evidence goes to show that the 

 nerve impulse is a form of motion, and hence of 

 energy, correlated with other forms of physical 

 energy. The nerve is, however, a very delicate 

 machine, and its total amount of energy is very 

 small. A tiny watch is a more delicate machine 

 than a water-wheel, and its actions are more de- 

 pendent upon the accuracy of its adjustment. 

 The water-wheel may be made very coarse and 

 yet be perfectly efficacious, while the watch must 

 be fashioned with extreme delicacy. Yet the water- 

 wheel transforms vastly more energy than the 

 watch. It may drive the many machines in a fac- 

 tory, while the watch can do no more than move 

 itself. But who can doubt that the watch, as well 

 as the water-wheel, is governed by the law of the 

 correlation of forces ? So the nervous system of 

 the living machine is delicately adjusted and eas- 

 ily put out of order, and its action involves only 



