ON  THE  PRESERVATION  OF  FLUID  EXTRACTS.  115 
water,*  and  then  dip  it  in  alcohol,  it  will  be  dry  instantly.  The 
whole  secret  is,  alcohol  has  the  power  of  abstracting  moisture 
from  membranes  and  all  similar  substances,  and  in  every  instance 
mentioned  by  Mr.  Thayer  is  this  its  office  ;  the  unpeeled  nutmeg, 
the  fresh  pear,  the  fermenting  currant  wine,  the  anatomical 
preparations  and  the  fruit  preserves  are  thus  by  alcohol  preser- 
ved against  further  decomposition  ;  ic  is  in  this  way  that  alcohol 
kills  the  vegetable  life  of  the  process  of  fermentation,  that  it 
destroys  the  proneness  of  animal  matter  to  putrefaction — and 
this  property  is  what  we  term  the  antiseptic  power  of  alcohol. 
But  there  are  other  forms  of  oxidation  which  do  not  announce 
themselves  by  the  appearance  of  foreign  organic  life  ;  they  pro- 
gress silently  and  uninterruptedly  when  once  begun,  as  long  as 
the  necessary  materials  have  not  been  used  up.  Though  these 
changes  are  less  visible,  nevertheless  we  must  assume  that  med- 
icinal organic  bodies  by  oxidation,  that  is  by  an  alteration  of 
their  chemical  composition,  likewise  alter  more  or  less  their  med- 
icinal properties.  Whichever  way  we  look  upon  the  various 
processes  of  deterioration,  we  will  always  find  oxygen  to  be  the 
powerful  enemy  we  must  try  to  conquer  in  keeping  all  our 
pharmaceutical  preparations.  We  therefore  inquire  which  of 
the  common  menstrua  used  in  pharmacy  are  most  apt  to  assist  in 
the  process  of  oxidation,  which  do  most  readily  absorb  the  at- 
mospheric gases  ? 
If  we  look  to  the  phenomenon  presented  by  liquids  before  the 
process  of  boiling,  we  can  partly  receive  a  clue  to  an  answer. 
Liquids,  when  they  expand  by  the  application  of  heat,  gradually 
lose  the  power  of  retaining  gases  in  solution,  and  long  before 
they  begin  to  boil,  small  bubbles  formin  different  parts,  but  more 
especially  in  the  neighborhood  and  directly  above  the  source  of 
heat,  where  the  temperature  is  highest :  these  are  air  bubbles, 
which  have  nothing  to  do  with  the  phenomenon  of  boiling,  which 
takes  place  after  a  considerable  quantity  of  air  has  been  ejected. 
Now  by  watching  liquids  being  heated  in  glass  vessels  to 
a  certain  temperature,  the  number  and  size  of  those  bub- 
bles will  enable  us  to  form  a  tolerable  estimate  of  the  propor- 
tion of  air  absorbed.  Such  a  rough  comparison,  of  course,  will 
never  approach  to  scientific  accuracy,  but  will  be  sufficiently  so 
for  experimental  use.    Alcohol  and  ether  if  at  a  low  tempera- 
