294  Chemistry  of  Pressor  Compounds.     { Am' fuiuyr*  m* 
lobes,  in  that  extracts  of  the  latter  favor  coagulation  of  the  blood, 
while  those  of  the  former  do  not. 
Paton  and  Watson15  have  found  that  extracts  of  the  pituitary 
gland  (pituitrin),  when  injected  intravenously  into  birds,  caused  a 
fall  in  blood-pressure,  and  that  after  repeated  injections  this  de- 
pressor action  failed  to  appear,  although,  at  times,  .such  injections 
caused  a  rise  in  blood-pressure.  In  birds  the  fall  in  pressure  was 
due  to  dilatation  of  the  abdominal  vessels,  and  might  be  neutralized 
by  more  powerful  ventricular  contraction. 
It  has  been  recently  shown  that  the  effects  of  extracts  of  the 
pituitary  gland  depend  to  some  extent  upon  how  rapidly  they  are  in- 
jected; thus  Miller  and  Miller  10  state  that  "  if  a  strong  saline  ex- 
tract of  the  posterior  lobe  of  the  hypophysis  be  injected  rapidly  a 
depressor  effect  only  may  be  obtained,  whilst  if  the  injection  be 
made  slowly  or  in  a  very  dilute  form,  the  pressor  effect  predomi- 
nates." 
On  purely  histological  evidence  Herring  17  separated  the  pituitary 
gland  into  an  anterior,  a  posterior,  and  an  intermediary  portion,  and 
argued  that  the  pressor  principle  originated  in  the  pars  intermedia. 
Recently  Lewis,  Miller  and  Matthews  18  have  found  that  the  more 
sharply  the  intermediary  portion  of  the  pituitary  is  removed  and 
extracted,  the  greater  the  rise  in  blood-pressure  which  results  from 
injection  of  such  extracts,  and  the  less  of  the  pars  intermedia  is 
used  the  less  the  rise.  Biedl  claims  that  the  pars  intermedia  can  be 
removed  comparatively  easily  in  thyreoidectomized  animals  and  that 
the  injection  of  aqueous  extracts  of  this  portion  of  the  gland  causes 
a  slowed  heart  with  a  rise  in  blood-pressure,  while  extracts  of  the 
pars  nervosa,  freed  from  the  pars  intermedia,  are  inactive,  save  in 
producing  a  slight  fall. 
15  Paton,  D.  H.,  and  Watson,  A.,  "  Actions  of  Pituitrin,  Adrenalin,  and 
Barium  on  the  Circulation  of  the  Bird,"  Jour  of  Physiol,  vol.  44,  p.  413  (1912). 
16  Miller,  J.  L.,  and  Miller,  E.  M.,  "  Effects  on  Blood-pressure  of  Organ 
Extracts,"  Jour,  of  Physiol.,  vol.  43,  p.  242  (1911). 
17  Herring,  P.  T.,  "  Histological  Appearances  of  the  Mammalian  Pituitary 
Body,"  Quart.  Jour.  Phys.,  vol.  1,  p.  1214  (1908). 
"Lewis,  D.,  Miller,  J.  L.,  and  Matthews,  S.  A.,  "Effects,  on  Blood- 
pressure  of  Various  Anatomical  Components  of  the  Hypophysis,"  Archives  of 
Int.  Med.,  vol.  7,  p.  785  (1911).  See  also  Schickele,  G.,  "  Ueber  die  Herkunft 
der  blutdrucksteigernden  Substanz  in  der  Hypophysis,"  Zcits.  f.  gesam.  Med., 
vol.  1,  p.  545  (1913). 
