The  most  important  change  effected  by  the  gastric  juice
is  that  of  the  proteids.  This  may  be  studied  either  on  natu-
ral juice  obtained  from  the  stomach  of  an  animal  through  an
opening  (gastric  fistula)  or  on  an  artificial  juice  prepared  by
extracting  the  mucous  membrane  of  a  fresh  stomach  with,
glycerine,  and  adding  a  large  quantity  of  dilute  (0.2^)  hydro-
chloric acid.  If  blood-fibrin  or  boiled  white  of  egg  be  placed
in  such  a  mixture  and  kept  at  a  temperature  of  about  38°  0.
(100°  F.)  these  bodies  swell,  become  transparent,  and  soon
dissolve;  and  all  other  solid  proteids  undergo  similar  changes.
