218  ON  THE  PRESERVATION  OF  FLUID  EXTRACTS. 
without  more  or  less  precipitation.  It  is  true  that  close  flannel 
will  strain  out  these  principles,  but  the  resulting  preparation 
will  not  be  of  much  worth.  If  they  are  suspended  only,  they 
are  "  sure  to  separate,  and  thus  detract  from  the  nicety  of  the 
preparation." 
I  find  on  the  next  page  an  admission  of  importance,  it  is 
this  :  that  a  certain  proportion  of  alcohol  tends  to  prevent  and 
arrest  vinous  and  acetous  fermentation  and  that  we  know  so 
little  concerning  "  natural  ferment,"  as  I  called  it,  that  in  near- 
ly all  cases  we  are  "  deprived  of  the  means  for  removing  it." 
Farther  on  the  subject  of  fermentation  is  again  alluded  to,  but 
only  to  remark,  that  «  the  necessary  quantity  of  sugar  will 
counteract  it,"  while  alcohol  will  not  do  it,  because  alcohol  has 
"  a  tendency  to  undergo  acetic  fermentation  through  the  influence 
of  sundry  vegetable  substances."  Although  the  subject  of  fer- 
mentation is  thus  lightly  passed  over,  I  deem  it  one  of  some 
importance,  and  worth  looking  at  for  a  moment. 
"  Natural  ferment  M  does  its  work  independently  of  oxygen. 
Vinous  fermentation  will  occur  equally  well  in  closed  or  open 
vessels.  Sugar  is  food  for  fermenting  substances  to  consume, 
the  only  substance  which  this  ferment  will  infect,  while  alcohol 
kills  its  action  and  stops  all  the  phenomena  of  vinous  fermenta- 
tion. But  it  is  said,  that  "  the  necessary  quantity  of  sugar  " 
will  accomplish  the  same  end.  Not  entirely.  The  variations 
of  temperature,  whether  induced  by  changes  of  weather,  sea- 
sons or  climate,  which  occur,  either  induce  fermentation  direct- 
ly, or  by  first  inducing  crystallization,  that  chief  enemy,"  in- 
directly give  the  exciting  substance  a  chance  to  act.  I  do  not 
see  how  difference  in  the  solubility  of  sugar  in  water  caused  by 
variations  of  temperature  occurring  at  different  seasons,  can  be 
a  more  serious  objection  than  fermentability,  when  the  latter  is 
a  direct  effect  resulting  from  the  former,  nor  do  I  see  why  differ- 
ence of  temperature  arising  from  different  seasons  is  a  serious 
objection  to  the  use  of  sugar,  when  an  argument  founded  upon 
the  same  variations  resulting  from  difference  of  climate,  is  pro- 
nounced untenable.  If  these  variations  of  temperature  affected 
only  the  specific  gravity  of  solutions  of  sugar,  we  should  hear 
very  little  about  them  ;  it  is  the  effects  following  this  difference 
in  specific  gravity  that  we  fear. 
