Am.  Jour.  Pharm.\ 
August,  19  iS.  J 
Colloidal  Metals. 
597 
doned.  The  solutions  of  Bredig,  as  described  above,  were  found  to 
be  eminently  suitable  for  therapeutic  use,  and  a  long  and  careful 
series  of  clinical  trials  were  made  with  these  with  good  results  in 
such  cases  as  pneumonia.  One  of  the  chief  effects  of  injection  of 
these  solutions  was  intensified  leucocytosis. 
As  has  already  been  stated,  this  action  appears  to  be  due  to  the 
fineness  of  the  metallic  particles,  and  to  their  vibratory  movement, 
and  it  has  been  demonstrated  that,  should  microscopic  examination 
show  these  particles  to  have  become  agglutinated  from  any  cause, 
their  therapeutic  activity  diminishes  in  direct  proportion  to  such 
agglutination. 
The  only  difficulty,  but  a  very  important  one,  which  at  first  at- 
tended the  employment  in  medicine  of  these  liquids  was  their  in- 
stability, the  particles  having  a  natural  tendency  to  agglutination. 
The  usual  methods  of  preservation  appeared  to  be  useless.  Steril- 
ization by  heat  caused  the  particles  to  agglutinate,  with  consequent 
loss  of  activity,  and  the  same  result  followed  the  addition  of  a  for- 
eign substance,  such  as  sodium  chloride.  Moreover,  when  injected 
into  the  blood,  the  salts  of  the  blood  serum  at  once  caused  this  ag- 
glutination and  nullified  any  therapeutic  action  such  solutions  might 
have. 
For  several  years,  therefore,  the  colloidal  metals,  while  they  had 
their  advocates  in  France,  were  regarded  by  British  practitioners 
more  as  a  therapeutic  curiosity.  Possibly  in  their  country  of  origin, 
where  their  freshness  might  be  confidently  relied  on,  they  found 
some  application,  but  the  instability  and  consequent  unreliability  of 
Bredig's  solutions  placed  them  beyond  the  region  of  practicle  thera- 
peutics. 
Later,  however,  a  method  was  found  of  overcoming  this  insta- 
bility. This  depends  on  the  curious  fact  that  an  unstable  colloid 
may  be  rendered  stable  by  the  addition  of  a  small  proportion  of  an- 
other colloid.  On  this  principle  these  metallic  solutions  may  be  pre- 
served and  isotonized  for  therapeutic  use. 
Under  the  name  of  collosols  an  English  firm  has  produced  a 
series  of  colloidal  solutions  of  metals  that  appears  to  meet  all  re- 
quirements. Their  stability  is  maintained  by  the  presence  of  an 
organic  colloid,  and  their  composition  and  physical  condition  remain 
unaltered  when  sodium  chloride  is  added  or  when  the  solution  is 
sterilized  by  boiling. 
