AmMayri8^7arm'}        Pharmacopceial  Preparations.  251 
freedom  from  contamination  afterwards,  is  to  have  it  freshly  dis- 
tilled ;  in  fact  as  regards  the  whole  of  the  preparations  of  the  Phar- 
macopoeia, they  should  be  as  freshly  prepared  as  possible,  and  the 
use  of  preservatives  should  be  avoided  unless  absolutely  necessary, 
but  from  a  practical  point  of  view  we  cannot  do  without  them.  For 
example,  the  public  demand  for  pills  is  now  that  they  must  be  well 
preserved  and  look  nice,  although  they  may  be  insoluble. 
Alcohol — The  most  common  preservative  used  officially  is  alcohol 
in  one  form  or  another ;  it  is  true  that  it  is  not  used  solely  as  a  pre- 
servative, but  as  a  solvent ;  it  enters  more  or  less  into  the  composi- 
tion of  nearly  all  our  tinctures,  liquid  extracts,  wines,  and  many  of 
our  official  solutions.  The  germination  of  most  of  the  micro-organ- 
isms occurring  in  aqueous  solutions  of  vegetable  and  animal  sub- 
stances is  inhibited  by  the  presence  of  20  per  cent,  by  volume  of 
absolute  alcohol,  but  it  is  inhibitory  only,  and  in  this  proportion  or  up- 
wards ;  it  is  in  no  way  germicidal,  as  on  evaporation  the  anaesthetized 
germs,  if  I  may  so  term  them,  readily  take  up  life  and  propagate. 
This  applies  to  most  of  the  volatile  antiseptics,  in  fact,  for  organic 
tissues,  such  as  strong  mineral  acids,  alkalies  and  halogens.  Excep- 
tions to  this  are  carbolic  acid,  creosote,  and  weak  solutions  of  corro- 
sive sublimate,  which  act  probably  by  coagulating  the  albuminous 
substance  of  the  microbe.  Wines  I  have  mentioned ;  unless  forti- 
fied, from  their  very  origin,  that  of  fermentation,  they  are  too  weak 
to  prove  of  useful  service  in  pharmacy,  and  in  fact  medical  wines  are 
anachronisms. 
Glycerin. — The  abuse  of  alcohol  has  led  those  who  take  extreme 
views  on  this  subject  to  endeavor  to  use  other  solvents  and  pre- 
servatives for  pharmaceutical  preparations.  Among  these,  avoiding 
ethylic  alcohol,  whose  physiological  properties  are  too  well  known, 
they  have  selected  glycerin,  which  is  but  another  alcohol  whose 
action  physiologically  is  not  so  well  ascertained,  nor  is  it  so  inhibi- 
tory to  the  development  of  micro-organisms.  Its  strong  solvent 
action  on  vegetable  extractives,  its  non-volatility,  and  its  stability  in 
other  respects  would  have  rendered  glycerin  a  useful  pharmacopceial 
solvent,  but  although  it  has  been  tried  again  and  again  and  was 
made  official,  more  especially  in  preparing  some  of  the  liquid 
extracts  of  the  United  States  Pharmacopoeia,  it  has  not  met  with 
general  acceptance.  It  nevertheless  has  a  curious  preservative 
action  over  some  inorganic  compounds  in  preventing  oxidation. 
