Am.  Jour.  Pharm. 
Mar.,  1880. 
The  Testing  of  Pep  sin . 
^57 
grams,  and  that  of  lactic  acid  from  8  to  12  grams  per  liter.  With 
hydrochloric  acid,  the  digestion  of  white  of  egg  takes  place  very  well 
in  liquors  containing  from  i  to  3  parts  per  1,000  of  real  acid,  the  most 
favorable  acidity  being  i  j-  part  per  looo. 
In  the  study  of  similar  phenomena  it  ought  never  to  be  forgotten 
that  the  digestion  in  the  stomach  goes  on  at  a  temperature  of  about 
40°C.  It  is,  therefore,  especially  at  this  temperature  that  the  test  of 
artificial  digestions  should  be  made.  It  might  happen,  in  fact,  that  an 
acid  solution,  acting  on  albumen  at  50°  or  6o°C.,  would  be  less  active  at 
40°C.  This  is  what  takes  place  with  lactic  acid,  which  at  a  concen- 
tration corresponding  to  2  or  even  3  per  1,000  of  real  hydrochloric  acid 
leaves  white  of  egg  in  great  part  undissolved  at  a  temperature  of  40°C., 
whilst  hydrochloric  acid  of  i  per  1,000,  in  the  same  conditions  of  time 
and  temperature,  dissolves  and  transforms  all  the  albumen. 
In  these  facts  is  found  the  experimental  demonstration  that  the  free 
acid  of  the  gastric  juice  is  hydrochloric  acid.  This  is  a  fact,  moreover, 
gained  to  science  by  the  remarkable  researches  of  M.  Richet,  who  has 
proved  that  the  acidity  of  the  gastric  juice  is  about  2  per  1,000  ;  that 
it  is  due  solely  to  hydrochloric  acid,  and  that  if  lactic  acid  is  found 
there  it  is  the  product  of  a  special  fermentation  which  the  food  has 
undergone  in  the  stomach. 
The  more  that  artificial  digestions  are  studied  the  more  evident 
becomes  the  similarity  which  exists  between  these  phenomena  and 
those  of  the  stomachal  digestion.  No  doubt,  the  stomach  absorbs 
during  the  digestive  period  a  portion  of  the  liquids  and  of  the  peptones 
they  contain,  and  this,  according  to  SchifF,  favors  digestion  consider- 
ably. The  movements  in  the  food  which  this  initiates  facilitate  the 
action  of  the  gastric  juice,  the  secretion  of  which  is  uninterrupted  ; 
but  it  is  no  less  true  that  in  experiments  in  vitro  it  is  easy  to  equal  and 
even  to  surpass  the  digestive  power  of  the  stomach. 
We  know  that  the  activity  of  the  gastric  juice  is  always  maintained 
within  certain  limits,  the  secretions  of  the  stomach  rapidly  re-establish- 
ing an  equilibrium  when  this  is  more  or  less  destroyed.  The  specific 
action  recognized  in  hydrochloric  acid  throws  light  on  the  rationale  of 
certain  medicines  and  the  troublesome  influence  exercised  by  some  sub- 
stances upon  the  act  of  digestion.  As  has  been  justly  remarked  by  M. 
Richet,  in  the  case  of  abnormal  fermentations  there  is  produced  a  great 
excess  of  lactic,  acetic  and  buytric  acids.  Hydrochloric  acid  is  no 
longer  secreted,  but  instead,  a  less  active  acid,  lactic  acid,  or  inactive 
