Am.  Jour.  Pharm. 
May,  1887. 
Action  of  Saliva  on  Starch. 
257 
with  saliva.  When  fermentation  was  complete,  the  reducing  power  of 
the  liquid  was  determined  by  means  of  Fehling's  solution.  The  saliva 
acts  only  on  the  starch  which  has  undergone  hydration,  and  it  was 
found  that  the  hydrating  action  of  water  begins  at  about  52 °,  and  in- 
creases somewhat  irregularly  up  to  74°,  beyond  which  point  an  in- 
creased temperature  exerts  no  sensible  effect. 
In  a  second  series  of  experiments,  the  water  and  saliva  were  mixed 
together,  heated  up  to  a  definite  temperature,  the  starch  added,  the 
temperature  maintained  for  about  3J  hours,  and  the  reducing  power 
of  the  liquid  was  then  determined.  The  results  show  that  saliva 
acts  on  starch  at  a  temperature  below  that  which  water  alone 
exerts  any  hydrating  action.  Feebly  acid  or  alkaline  liquids,  or 
solutions  of  sodium  chloride  or  phosphate  have  no  action  on  amylose 
at  temperatures  below  53°,  and  saliva  in  which  the  ferment  has  been 
destroyed  by  boiling  is  scarcely  more  active.  It  follows  that  it  is  the 
diastase  in  the  saliva  which  assists  the  hydrating  action  of  the 
water. 
At  the  temperature  at  which  water  alone  begins  to  convert  starch 
into  a  hydrate  saccharifiable  by  saliva  at  the  ordinary  temperature, 
water  mixed  with  saliva  has  a  more  energetic  action  than  when  water 
and  saliva  are  allowed  to  act  successively  in  the  way  described.  The 
difference  diminishes,  however,  as  the  temperature  approaches  58°,  at 
which  point  the  two  actions  are  equal.  At  higher  temperatures  the 
action  is  greater  if  the  water  alone  is  heated,  and  the  saliva  is  after- 
wards added  to  the  cooled  liquid,  than  when  the  saliva  and  water  are 
heated  together,  since  the  high  temperature  destroys  the  diastase  in 
the  saliva. 
Potato  starch  was  heated  with  saliva  and  water  at  different  tem- 
peratures for  different  periods  of  time.  At  temperatures  below  57°, 
the  amount  of  reduction  increases  with  the  temperature  and  also  with 
the  time,  but  is  not  proportional  to  the  latter.  At  temperatures 
above  57°,  however,  the  action  continues  to  increase  with  the  tem- 
perature, but  attains  its  maximum  in  about  five  hours,  and  pro- 
ceeds very  little  further  even  if  the  experiment  is  prolonged  to  thirty 
hours. 
The  hydrating  action  of  water  alone  increases  with  the  tempera- 
ture, and  is  practically  complete  after  five  hours,  increasing  but  little 
if  the  experiment  is  continued  for  thirty  hours.  The  hydrating  action 
of  the  water  is  independent  of  the  mass  of  the  water. 
17 
