Difference  Theory  of  Muscle  and
Nerve  Currents. — A  theory  proposed
to  explain  the  cause  of  the  electric  cur-
rents in  living  tissues,  by  an  alteration  or
change  in  the  protoplasm,  by  injury,  by
differences  of  temperature,  or  by  polari-
zation.
Differential  Coils.— Coils  that  are  differ-
entially wound,  or  that  act  differentially.
Differential  Compound  Motor.  —  (1)
A  compound  motor  in  which  the  mag-
neto-motive force  of  the  working  current
is  opposed  to  the  magneto-motive  force  of
the  shunt  excitation,  for  the  purpose  of
maintaining  the  speed  constant  under  all
loads.  (2)  A  compound-wound  contin-
uous-current motor.
Differential  Electric  Arc-Lamp.— A
term  formerly  employed  for  a  derived-
circuit  arc-lamp,  in  which  the  lifting
magnet  either  consists  of  a  core  or  sole-
noid wound  with  series  and  shunt  coils,
or  of  two  separate  and  opposed  cores,  one
of  which  contains  the  series  and  the  other
the  shunt  winding.
Differential  Electric  Bell. — An  electric
bell  whose  magnetizing  coils  are  differ-
entially wound.
Differential  Electro-Dynamometer. —
(1)  A  double  dynamometer  with  two  mov-
ing coils  rigidly  connected  and  oppositely
acted  on,  so  that  the  movement  of  the  sus-
pension system  can  be  reduced  to  zero  by
electrical  adjustments  made  while  the  in-
strument is  under  operation.  (2)  A  dyna-
mometer for  measuring  the  difference
between  two  electro-dynamic  forces.
Differential  Electro-Magnet.— A  differ-
entially-wound electro-magnet.
Differential  Equation. — An  equation
connecting  quantities  into  which  one  01
more  differential  coefficients  or  differ-
entials enter.
Differential  Galyanometer.— A  gal-
vanometer containing  two  coils,  so  wound
as  to  tend  to  deflect  its  needle  in  opposite
directions.
Dif.]


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[Dil.
