258  Pharmacopceial  Preparations.  {^i^m™' 
Benzoic  Acid. — For  preserving  lard  and  some  official  ointments, 
the  melted  fats  are  macerated  with  powdered  benzoin,  by  which 
means  they  obtain  an  agreeable  odor  and  become  impregnated  with 
benzoic  acid.  Both  these  tend  to  preserve  the  fats  from  becoming 
rancid.  But  in  using  these  fats  for  preparing  the  ointments  of  the 
alkaloids,  apparently  some  change  takes  place ;  they  become  dis- 
colored, and  in  the  case  of  cocaine  we  know,  as  I  have  before  men- 
tioned, a  comparatively  inert  compound  of  benzoyl-ecgonine,  etc., 
is  formed,  so  that  the  use  of  benzoated  lard  is  to  be  avoided  for  pre- 
paring these  ointments. 
Paraffin  Basis. — Where  quick  absorption  is  not  required,  the  pre- 
servative action  of  the  soft  paraffins  renders  them  all  that  can  be 
desired,  as  also  is  oil  of  theobroma  for  suppositories. 
Aromatic  Waters  and  Essential  Oils. — The  oils  of  clove,  cinnamon, 
peppermint,  and  many  others  are  preservatives ;  so  are  their  aqueous 
solutions,  but  I  can  only  mention  them. 
Heat  and  Cold. — A  gentle  heat  assists  the  incubation  of  nearly  all 
micro-organisms ;  a  greater  heat,  that  of  boiling  water  for  example, 
is  a  sterilizer;  whereas  a  still  higher  temperature  is  a  disorganizer, 
and  is  destructive  to  all  organic  growths.  Cold,  on  the  contrary, 
the  freezing  point  of  water  and  below,  as  a  rule,  is  only  inhibitory 
to  the  development  of  the  lower  organisms,  their  vitality  is  but  sus- 
pended, and  they  spring  into  life  again  with  the  first  application  of 
a  gentle  warmth.  It  may  appear  irrelevant  to  my  subject,  but  the 
important  bearing  preservatives  have  on  our  food  supplies,  including 
frozen  meat,  makes  them  of  great  importance  commercially.  In 
fact,  in  viewing  the  pharmaceutical  aspect  of  preservatives,  I  have 
but  touched  the  fringe  of  the  subject  of  their  utility.  Without  the 
aid  of  boric  acid  and  other  preservative,  many  of  our  articles  of  daily 
food  would  be  at  famine  prices.  In  such  a  condensed  population  as 
that  of  London,  it  would  now  be  almost  impossible  to  supply  the 
necessary  quantities  of  butter,  milk  and  fish  in  a  fresh  condition. 
We  have  long  been  dependent  to  a  great  extent  on  the  importation 
of  flour  and  corn.  The  same  has  now  become  the  case  in  regard  to 
our  animal  food  products. 
