76  Digestion  of  Mineral  Substances. .     { A%{Ti  mT' 
In  closing  his  article,  Dr.  Dupuis  solicits  for  the  decoction  of  the 
bark  of  Tag  alder  a  trial  from  all  those  who  may  be  interested  in  the 
development  of  the  medical  remedies  of  our  own  country. — Medical 
Press,  Jan.  3,  1872. 
NOTE  ON  THE  DIGESTION  OF  MINERAL  SUBSTANCES* 
By  Richard  V.  Tuson,  f.  c.  s. 
Professor  of  Chemistry  in  the  Royal  Veterinary  College. 
Physiologists  and  chemists  have  hitherto  entertained  the  belief  that 
the  principal,  if  not  the  sole  function  of  the  pepsin  and  acid  contained 
in  the  gastric  juice  is  to  render  soluble  the  albuminoid  constituents  of 
food,  and  thus  prepare  them  for  the  subsequent  process  of  absorption. 
Conceiving,  however,  that  it  would  be  extremely  interesting  to 
study  the  effect,  if  any,  of  the  solvent  constituents  of  the  gastric 
juice  upon  mineral  substances,  especially  those  employed  as  medicines, 
I  have  set  myself  the  task  of  investigating  this  subject.  The  inquiry 
is  yet  but  in  its  infancy  ;  nevertheless  the  results  already  obtained  are 
sufficiently  positive  and  striking  to  induce  me  to  "claim  date"  by 
placing  on  record  the  following  experiments  : — 
Experiment  1. — A  mixture  of  calomelf  and  distilled  water  contain- 
ing 2  per  cent,  of  hydrochloric  acid. 
Experiment  2. — A  mixture  of  calomel,  pepsin, \  and  distilled  water. 
Experiment  3. — A  mixture  of  calomel,  pepsin,  and  distilled  water, 
containing  2  per  cent,  of  hydrochloric  acid. 
These  mixtures  were  placed  in  glass  vessels,  and  kept  at  38°  C. 
(100*2  F.),  i.  e.  at  about  the  temperature  of  the  body,  for  twenty- 
four  hours,  during  which  time  they  were  occasionally  stirred  or 
shaken.  They  were  then  thrown  on  to  filters  of  Swedish  paper,  and 
the  filtrates  saturated  with  sulphuretted  hydrogen.  The  filtrates  from 
Experiments  1  and  2  remained  unaltered.  The  filtrate  from  Experi- 
ment 3  yielded  a  precipitate  of  sulphide  of  mercury. 
The  results  of  these  experiments  therefore  show  that  neither  dilute 
hydrochloric  acid  (2  per  cent.)  nor  pepsin  alone  is  capable  of  dissolv- 
ing calomel,  but  that  when  these  agents  are  mixed  they  do  affect  its 
*  Reprinted  from  the  Lancet. 
fThe  calomel  employed  in  all  the  experiments  was  previously  tested  as  to  its 
purity. 
X  Pepsina  porci,  prepared  by  Messrs.  Bullock  and  Reynolds. 
