7o8 
Theories  of  Blood-Coagulation 
5  Am.  Jour,  Pharm. 
(       Oct.,  1921. 
No  thrombin  is  produced  when  platelets  are  added  to  serum  that 
has  been  exposed  to  a  temperature  of  about  56°  C.  On  the  contrary, 
cytozyirie,  the  active  principle  of  platelets,  may  be  heated  to  a  hun- 
dred degrees  and  even  higher  without  losing  its  properties ;  cytozyme 
is  thermostable  and,  furthermore,  can  be  easily  extracted. 
A  thick  emulsion  of  platelets,  treated  with  a  large  excess  of 
absolute  alcohol,  gives  an  extract  from  which,  by  evaporation  a 
residue  is  obtained  which  is  soluble  in  alcohol,  ether,  toluol  and 
chloroform  but  insoluble  in  acetone,  thus  exhibiting  the  characteris- 
tics of  lipoids,  and  especially  of  lecithin.  This  residue  acts  as  a  very 
powerful  cytozyme. 
As  we  were  able  to  show  eight  years  ago  traces  of  this  lipoid 
behave  exactly  as  do  platelets,  generating  thrombin  when  added  to 
serum,  hastening  the  coagulation  of  recalcified  oxalated  plasma  or 
causing  the  coagulation  of  spontaneously  non-coagulable  bird's 
plasma.  The  same  lipoid,  possessing  exactly  the  same  properties  may 
be  extracted  from  tissues,  from  muscle  for  example.  Cytozyme  is 
thus  a  lipoid. 
These  facts  having  been  obtained  about  cytozyme,  what  is  sero- 
zyme?  Serozyme  is  certainly  furnished  by  the  plasma,  not  by  the 
cells.  Platelets  contain  cytozyme;  they  yield  thrombin  when  mixed 
with  serum  but  they  are  never  able  to  liberate  thrombin  when  kept 
in  physiological  solution  or  in  distilled  water,  even  in  the  presence 
of  calcium  salts.  They  consequently  contain  only  one  of  the  mother- 
substances,  not  both  of  them.  The  liability  of  serozyme  towards 
heat  allows  us  to  presume  that  this  substance  is  of  an  albuminous 
nature.  Its  fragility  would  be  a  very  serious  hindrance  to  its  isola- 
tion, but  for  one  of  its  properties — a  really  fortunate  one.  The 
serozyme  shows  a  strong  tendency  to  adhere  to  mineral  precipitates, 
barium  sulphate  or  calcium  fluoride  for  example.  This  is  the  rea- 
son why.  as  I  discovered  many  years  ago  with  Gengou,  those  pre- 
cipitates, added  to  oxalated  plasma  wholly  suppress  in  the  latter  the 
property  of  coagulating  by  subsequent  recalcification ;  one  of  the 
mother-substances,  the  serozyme,  which  is  absolutely  requisite  for 
the  production  of  thrombin  and  consequently  for  coagulation,  has 
been  entirely  removed.  I  have  found  more  recently,  in  conjunction 
with  Delange,  that  tricalcic  phosphate  is  especially  powerful  as  an 
absorbent.  When  diluted  in  physiological  solution,  this  substance 
gives  a  rather  gelatinous  emulsion,  a  very  slight  quantity  of  which, 
