ANIMAL AND VEGETABLE 245 



CHAPTER XVIII 

 OHM'S LAW 



IN ITS APPLICATION TO THE HUMAN BODY 



As I have frequently mentioned Ohm's law, and have 

 said that all body deflections must conform to it, I will, for 

 the guidance of the medical practitioner, explain it so far 

 as may be necessary. I have given it, briefly, as C = ^- 



that is, the current at any point is equal to the electro- 

 motive force divided by the resistances in circuit at that 

 point, assuming both electromotive force and resistances 

 to be constant. But that is only a part of Ohm's law, and 

 we must ponder it further to see whether it in any way 

 conflicts, or in every way agrees, with observed phenomena. 



As most of my readers will be aware, the unit of electro- 

 motive force is called a volt, that of resistance an ohm, and 

 that of current an ampere. The quantity of electricity 

 which flows per second in a current of one ampere is known 

 as a coulomb, and the capacity of a condenser in which a 

 charge of one coulomb causes a potential of one volt is 

 said to be a Farad. 



To put it in terms of hydrostatics, with which everyone 

 will be familiar, E is the head of water (pressure) ; R is 

 the resistance offered to flow by the inner perimeter of the 

 pipe (in the inverse ratio to the sectional area of the pipe) ; 

 C represents the quantity of water flowing through the 

 pipe at any point, and is, obviously ~ ; while the coulomb 

 may be said to be the unit of effective discharge, 



