Am.  Jour.  Pharm. 
Mar.,  1880. 
The  Testing  of  Pepsin. 
159 
would  give  5  to  7*5  grams  of  acid  expressed  as  lactic  acid,  whilst  the 
action  would  be  much  weaker  in  the  presence  of  the  latter  solvent. 
I  would  also  remark  that  the  acidity  of  the  i  per  1,000  in  HCl, 
which  is  favorable  to  the  solution  of  coagulated  albumen,  is  not  suffi- 
cient for  the  easy  transformation  of  fibrin.  In  order  to  approach  phy- 
siological condition  I  would  propose,  therefore,  to  employ  1*50  gram  of 
real  HCl  per  liter  in  the  testing  with  coagulated  white  of  egg  and  3 
grams  per  r,ooo  for  testing  with  fibrin. 
It  may  be  asked  whether  it  is  not  possible  to  render  the  testing  of 
pepsin  more  practical  by  diminishing  the  time  of  operating.  Nothing  is 
more  easy.  In  heating  during  six  hours  instead  of  twelve  about  twice 
as  much  pepsin  is  required  for  the  transformation.  Again,  in  heating 
during  six  hours  at  40°C.,  instead  of  twelve  hours  at  50°C.,  nearly 
eight  times  the  quantity  of  pepsin  is  required  to  obtain  the  same  result. 
This  great  influence  exercised  ^by  temperature  renders  it  necessary 
that  a  standard  for  operating  should  be  fixed  in  an  exact  manner.  The 
Commission  of  1865,  in  recommending  to  heat  to  from  40°  to  45°, 
was  not  sufficiently  precise  upon  this  important  point. 
I  have  stated  that  there  is  an  essential  difference  between  the  solu- 
tion of  fibrin  and  its  transformation  ;  the  following  experiments  demon- 
strate this  very  clearly  : 
■  A  pepsin  prepared  in  my  laboratory,  which  dissolved  and  transformed 
in  twelve  hours  at  a  temperature  of  50°C.  six  hundred  times  its  weight 
of  fibrin  in  a  liquor  containing  4  per  1,000  of  real  HCl,'dissolved  in 
the  same  conditions  : 
1,200  times  its  weight  of  fibrin  in     .  .1  hour. 
2,400  "  "  "  ,1  hour  10  minutes. 
4,800  "  "  "  .           .        I  hour  15  minutes, 
9,600  "  "  "  .1  hour  45  minutes. 
19,200  *'  "  "  .           .        2  hours  10  minutes. 
It  was  not  thought  necessary  to  carry  the  experiment  further. 
An  identical  experiment  was  made  with  lactic  acid  in  the  proportion 
of  0*40  gram  to  25  cc.  or  16  grams  per  liter.  Although  the  same  pepsin 
transformed  in  these  conditions  only  one  hundred  times  its  weight  of 
fibrin,  instead  of  six  hundred  times,  as  in  the  preceding  experiment,  it 
was  found  that  it  dissolved — 
1,200  times  its  weight  in        .  .  .30  minutes. 
2,400  "           "  .           .           .  I  hour  15  minutes. 
4,800  an  ...  I  hour  30  minutes. 
9,600  4  hours. 
19,200  «           <i  ...  5  hours. 
