lo/ta's  Researches :  The  Theory  of  Contact  and  Chemic  Action. — Among
those  who  were  stimulated  by  the  discovery  of  Galvani  was  Volta,  profes-
sor of  physics  in  Favia,  Italy,  who  had  already  been  long  distinguished
as  an  electric  experimenter,  and  who,  in  the  knowledge  of  this  special
branch,  was  far  superior  to  Galvani.
At  first  Volta  accepted  Galvani's  theory  of  animal  electricity,  but  sub-
sequent research  caused  him  to  doubt  its  truth.  He  observed  that  it  was
only  by  means  of  heterogeneous  metals  that  muscular  contractions  could
invariably  be  produced,  and  hence  he  denied  the  existence  of  animal
electricity,  explaining  the  phenomenon  of  muscular  contractions  through
the  influence  of  the  artificial  electricity  excited  by  a  heterogeneous  metallic
combination.*

Galvani  then  not  only  demonstrated  that  contractions  could  readily  be
caused  by  exactly  homogeneous  metals,  but  that  the  phenomenon  was  pro-
duced by  the  simple  contact  of  nerve  and  muscle.  His  manner  of  experi-
menting was  as  follows:  The  leg  of  a  frog,  denuded  of  its  skin,  had  its
sciatic  nerves  cut  at  their  exit  from  the  vertebral  column.  The  nerves
thus  denuded  were  taken  gently  up  by  some  non-conductor  and  made  to
touch  one  of  the  muscles,  when  the  leg  would  immediately  become  con-
vulsed. Volta  endeavored  to  prove  that  the  concussion  caused  by  the
contact  of  nerve  and  muscle  was  the  cause  of  the  electric  current  thus  pro-
duced: but  Galvani  conclusively  demonstrated  that  such  could  not  be  the
case,  by  placing  a  non-conductor  between  the  two  tissues,  when  no  action
could  be  excited  in  the  leg.  He  went  further,  and  at  last  succeeded  in
producing  muscular  contractions  when  only  the  nerves  of  non-prepared
ere  brought  in  contact.
