114  ON  THE  PRESERVATION  OF  FLUID  EXTRACTS. 
Thayer,  but  I  believe  it  does  not  cover  the  whole  of  that  ground 
which  he  has  assigned  for  it.  It  is  doubtless  true  that  the  pres- 
ence of  a  certain  proportion  of  alcohol  tends  to  prevent,  or, 
where  it  has  commenced,  to  arrest  the  progress  of  vinous  and 
even  acetic  fermentation,  but  vegetable  matter  of  itself  will  not 
undergo  these  changes,  unless  principles  are  present  which  are 
able  to  act  as  ferments.  Therefore,  if  we  could  succeed  in  re- 
moving such  fermentative  matter,  the  liquid,  whether  alcoholic  or 
aqueous,  could  not  undergo  either  fermentation.  Of  this  matter, 
however,  as  it  occurs  in  different  plants,  we  know  as  yet  too  little, 
and  in  nearly  all  cases  we  will  for  this  reason  be  deprived  of  the 
means  for  removing  it. 
But  on  the  other  hand,  vinous  and  acetic  fermentation  are  not 
the  only  alterations  to  which  organic  matter  is  subject,  a  trans- 
formation of  the  elements  and  consequent  change  taking  place 
wherever  the  air  has  access,  but  under  different  circumstances 
this  change  will  be  different.  Berzelius,  on  speaking  of  the  met- 
amorphoses of  organic  bodies,  uses  the  following  language  : 
"  Mixed  organic  bodies,  when  moist  and  at  a  certain  temperature 
left  to  themselves,  undergo  changes,  the  end  of  which  appears  to 
be  to  decompose  them  into  other  combinations  of  the  elements, 
and  ultimately  after  a  shorter  or  longer  period,  to  transform  them 
into  inorganic  compositions."  And  again  in  another  place  : 
"  Nature's  aim,  it  seems,  is,  not  to  grant  stability  to  anything  of 
an  organic  composition,  but  to  gradually  destroy  it.  Bodies 
that  are  perfectly  pure,  may  in  the  solid  state  be  kept  unal- 
tered, and  inmost  cases  for  an  indefinite  period,  oftentimes,  their 
being  surrounded  by  or  dissolved  in  water,  has  no  destructive 
influence  on  them.  But  if  two  or  more  bodies  are  mixed  and  ex- 
posed to  the  influence  of  moisture  and  air,  a  process  of  meta- 
morphosis is  induced,"  &c. 
The  change  in  the  organic  matter  is  caused  by  oxygen,  it  is 
an  oxidation  to  which  as  we  notice  it  in  ordinary  life  accompa- 
nied by  different  phenomenon,  we  apply  different  names.  Mould 
putrescence,  fermentation,  &c.  are  such  changes,  at  the  same  time 
accompanied  by  the  development  of  organic  life.  Alcohol  has 
the  power  to  prevent  or  retard  these  changes,  and  the  cause  for 
this  power  may  be  easily  illustrated  by  the  following  well  known 
simple  experiment.  Wet  a  beef  or  hog's  bladder  thoroughly  with 
