ANIMAL AND VEGETABLE 97 



same in amount, but their potential differences will vary in 

 proportion to the plate areas/,/!, and/ 2 . 



In a the charge has only a surface of 2 microfarads over 

 which to diffuse itself ; consequently, as this surface is the 

 smallest of the three, the potential difference of its plates 

 will be the maximum. In b it will be only half as great as 



in a, while in c it can only be equal to or -. 



2 3 



The sum of the potential differences should equal the 

 E.M.F. of the battery, and would work out as follows : 



a = 1-091 volts (about) 

 b = 0-545 volt 

 c = 0-364 

 Total 2-000 volts 



It will thus be seen that to raise a to the same potential 

 difference as c, only one-third of the charge it has accepted 

 in series would be required. Similarly the joint capacity 

 of any number of condensers of equal capacity connected 

 in series is the capacity of any one of them divided by their 

 number. 



It will also be seen why, if the sarcomeres of voluntary 

 muscular tissue are joined up in series, it can only be in 

 limited groups of them, otherwise capacity and potential 

 difference would approach the vanishing point before the 

 initial impulse had travelled very far. That connection is 

 made in this manner, i.e., in series -par all el, will be apparent 

 when study is made of the terminations of nerves in 

 muscle (p. 150). 



We have now learned some very important facts, viz. 



(1) That capacity varies directly as the surfaces of 

 the opposing plates, (2) that the velocity of the current is 

 in the inverse ratio to the capacity, and (3) that capacity 

 varies inversely as the distance between the plates. That 

 being so, it follows : (1 ) the larger the plate-area the greater 



H 



