LITE AND ELECTRICITY 21 



as the carrier of energy. The muscular fibres of the heart 

 are undoubtedly electrical in character and form part of 

 an automatic system. The energy supplied to them is 

 governed and controlled in a very wonderful way, because 

 although the oxygen intake of man is halved during sleep 

 the pressure, in normal health, never varies in its proportion. 



To fully comprehend this we must recall the fact that by 

 reason of its greater blood supply the brain is the seat of 

 highest potential. From the brain issue two branches 

 of the vagus nerve, called the cardiac branches. Their 

 function is akin to that of a gas governor which when 

 the water is sufficiently hot automatically lowers the flame, 

 or increases it when the temperature of the water falls. 

 Now the oxygen intake being halved at night the pressure 

 of the heart's energy would, failing an arrangement of this 

 kind, be halved also, but inasmuch as the inhibiting current 

 from the brain along the cardiac branches of the vagi falls 

 in the same proportion, the pressure of the energy supplied 

 to the heart is unaltered. 



It will be noted that I hold the human body to be a com- 

 plicated piece of electrical apparatus, the lungs providing 

 the battery and the nerves being, to all intents and purposes, 

 insulated wires. Of what, it will be asked, does their insula- 

 tion consist ? It consists of several substances, but mainly 

 of the sheaths of the medullated and the lipoid coatings 

 of non-medullated nerves ; the skin resistance serving to 

 maintain the body potential within limits consistent with 

 the safety and comfort of the individual. 



As regards the vegetable world, let us, as we have done 

 with the human body, go back as far as we can, to the 

 beginning of things, and study the seed ; selecting, for 

 illustration, one with which we are familiar and which is 

 large enough for its structure to be seen with the naked eye. 

 We will take an edible chestnut in its pod, for it is very 

 similar in appearance to a foetus in the womb and for that 

 reason more than ordinarily interesting. 



In normal conditions of weather the air is the positive 

 and the earth the negative terminal of Nature's electrical 

 system. Everything growing in the earth is negatively 



