Through  one  end  of  the  muscles  push  two  pins  attached  to  wires  to
act  as  electrodes.  Some  prefer  the  two  sartorii  muscles,  fastened
together,  the  one  lying  on  the  other  and  fixed  by  means  of  pins.
(c.)  Stimulate  with  a  maximal  break  induction  sliock  and  note
that  two  curves  on  different  abscissae  are  obtained,  the  one  a  little


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PRACTICAL  PHYSIOLOGY.
[XLIIL


later  than  the  other.  The  distance  between  the  two  indicates  tlie
time  taken  by  the  contraction  to  pass  from  the  one  lever  to  the
otlier.     Test  the  effect  of  cold  normal  saline.
Fia.  150.— Marey  3  Registering  Tambour.     Metallic  capsule,  T,  covered  with  thin  indiS'
rubber,  and  bearing  an  aluminium  disc,  which  acts  on  the  writing-lever,  H.
3.  Thickening  of  a  Muscle  during  Contraction.
(a.)  Arrange  a  Marey's  tambour  to  write  on  a  pendulum-myograph  (fig.
150).
(6.)  Fix  Marey's  pince  mr/ographigue  (fig.  151)  so  as  to  compress  the
adductor  muscles  between  the  thumb  and  the
metacarpal  bone  of  the  index-finger,  keeping  the
two  arms  together  with  an  elastic  band.  Or  use
a  pair  of  toy  bellows,  to  the  arms  of  which  plate-
like electrodes  are  fitted  and  connected  with  bind-
ing screws.  Keep  the  handles  of  the  bellows
pressed  upon  the  adductor  muscles  by  means  of
an  elastic  band.  Connect  the  receiving  tambour
of  the  pince  or  the  nozzle  of  the  bellows  with
the  recording  tambour,  introducing  a  valve  or
T-tube  with  a  screw  clamp  into  the  connecting
elastic  tube,  to  regulate  the  pressure  of  air  within
the  system  of  tubes.
('•.)  Arrange  an  induction   machine   with   the
trigger-key   of  the   pendulum-myograph   in   the
])nniary  circuit,  and  the  pince  or  bellows  in  the
secondary.     Take  a  tracing.     The  time  relations  of  the  contraction  are  de-
termined in  tlie  manner  already  stated  (Lesson  XXXV IL).
