302  Chemistry  of  Pressor  Compounds.     { Am'jui°yuri9i4arm' 
uninjured  by  hydrogen  sulphide  alone,  hence  the  active  pressor  com- 
pound must  have  been  carried  down  with  the  lead  sulphide,  but 
as  yet  we  have  been  unable  to  recover  it  from  the  lead  sulphide  pre- 
cipitate. From  this  precipitation  and  from  the  fact  that  it  is  com- 
pletely removed  or  destroyed  by  animal  charcoal  we  argued  a  high 
molecular  weight,  although  this  does  not  necessarily  follow.  After 
thorough  precipitation  with  lead  subacetate  and  freeing  from  lead 
with  phosphoric  acid  the  filtrate  gave  no  biuret  reaction,  but  gave  a 
reaction  with  Folin's  hydroxy-phenyl  reagent.  After  lead-sub- 
acetate  precipitation  and  removal  of  the  lead,  neither  zinc  sulphate 
nor  ammonium  sulphate  (saturated  solution)  gave  a  precipitate. 
In  connection  with  one  of  our  students  we  had  begun  some  work 
with  Caviar  pepton  *  and  found  that  the  intravenous  injection  into 
a  dog  of  a  few  milligrams  of  it  would  produce  a  marked  and  per- 
sistent rise  in  blood-pressure.  This  at  once  suggested  that  there 
was  a  pepton  which  would  cause  a  rise  in  blood-pressure,  or  that  the 
rise  which  followed  the  injection  of  Caviar  pepton  was  due  to  cal- 
cium or  barium,  supposedly  used  in  neutralizing  the  acid  used  in  the 
hydrolysis,  or  to  amino-compounds  arising  in  the  formation  of  the 
pepton,  or  to  albumose,  or  to  some  other  unknown  compound  formed 
along  with  peptons. 
We  had  noticed  that  an  iodine  and  potassium  iodide  solution 
would  produce  a  precipitate  from  certain  pituitary  extracts,  and  that 
this  precipitate,  after  decomposing  with  sulphurous  acid,  was  physio- 
logically active,  while  Fiihner  has  shown  that  various  active  prin- 
ciples were  obtained  from  the  phosphotungstic  acid  precipitate,  and 
Aldrich  has  obtained  an  active  principle  by  means  of  picric  acid. 
Now  certain  so-called  peptons  give  precipitates  with  phospho- 
tungstic acid,  iodine  and  potassium  iodide  solution  and  picric  acid, 
and  produce  an  immunity,  or  rather  a  tolerance,  to  a  second  injec- 
tion and  interfere  with  coagulation  of  the  blood.  Pick  and  Spiro  42 
showed  that  the  depressor  action  on  blood-pressure  and  the  anti- 
coagulant action  of  Witte's  pepton  were  not  due  to  peptons  or  albu- 
moses,  but  to  some  other  compound  associated  with  them;  as  Pick 
*  Note. — Supplied  by  the  courtesy  of  the  Hoffmann-La  Roche  Chemical 
Works  of  Grenzbach,  Germany,  through  their  New  York  branch. 
42  Pick,  E.,  and  Spiro,  K.,  "  Ueber  gerinnunghemmende  Agentien,"  Zeits. 
f.  Physiol.  Chem.,  vol.  31,  p.  235  (1900). 
