THE ANIMAL A MACHINE 199 



layers and to alternate them, as well as to insert salt- 

 solution layers. A set-up of this type is capable of pro- 

 ducing electric charges of an intensity which compares 

 favorably with the living battery of the eel. Another 

 secret has thus been snatched from nature; batteries with- 

 out any metal can be made artificially which means that 

 the living battery can be better understood. Continued 

 investigation and closer comparison discloses numerous 

 similarities between these artificial fat batteries and the 

 batteries existing in living tissues. 



We can now understand why the comparison of a nerve- 

 fiber, consisting of fat, with a battery plate, consisting of 

 metal, is justifiable. Fat-layers act like metals in several 

 ways with respect to electrical properties. This is why the 

 animal organism can behave like an electrical mechanism, 

 although of a type wholly different from the electrical 

 apparatus which is in practical use for various purposes. 



10. THE MODE OF ACTION OF POISONS AND DRUGS 



Every driver of a car knows that his battery must be 

 rilled up periodically with pure distilled water. Tap water, 

 which contains traces of ordinary table salt, should never 

 be used. Traces of this salt if added to the battery interact 

 chemically with the positive plate and destroy it. Corro- 

 sive chlorine gas is formed which in turn passes to the 

 nearby negative pole, thus destroying the entire battery 

 beyond repair. 



We have seen that a nerve impulse is a traveling elec- 

 trical charge and that the living organism can produce 

 electric charges like an electric battery. If the crude lead 

 battery of our cars is so sensitive to salt, should we not 

 expect the living battery with its traveling electric charges 

 to be still more likely to be put out of commission by 

 poison? We realize, of course, that the lead battery and 

 the living battery differ in other respects. Living organ- 

 isms are not poisoned by ordinary salt which "kills" the 



