PHYSIOLOGICAL  EXHAUSTION  OF  BEER  YEAST,  ETC.  161 
leaves,  after  having  remained  so  long  inclined  to  the  ground, 
raise  themselves  and  approach  the  conical  bud,  as  if  to  cover 
and  protect  it.  Then  there  is  a  very  apparent  and  gradual 
movement,  seeming  to  obey  a  will.  The  bud  lengthens  with 
surprising  rapidity,  and  a  flower-stalk,  five  or  six  metres  in 
length,  is  soon  formed.  The  work  of  reproducing  the  seed  is 
thus  accomplished,  and  it  is  by  preventing  this,  that  the  Indians 
procure  an  ample  harvest  of  the  sweet  sap,  by  fermenting  which, 
they  prepare  pulque,  their  favorite  intoxicating  drink.  One 
agave  plant,  in  the  environs  of  Cholula,  yields  in  four  or  five 
months  nearly  one  cubic  metre  of  sweet  liquid,  after  which  it 
dies  exhausted,  as  it  would  also  die  exhausted,  were  the  stalk 
allowed  to  develop  and  bear  flowers  and  fruit.  An  agave  yields 
in  four  months  about  100  kilogrammes  of  glucose,  prepared  and 
preserved  by  its  leaves  for  years.* 
There  is  no  doubt  as  to  the  origin  of  this  glucose ;  it  proceeds 
from  the  carbonic  acid  and  water  decomposed  by  the  leaves. 
To  conclude,  I  trust  my  experiments  will  enable  me  to  dispute 
the  direct  formation  of  saccharine  matter  by  the  green  parts  of 
vegetables  exposed  to  the  sun. — Lond.  Chem.  News,  Dec.  22, 
1865,  from  Comptes  Hendus,  Ixi.,"  664.  • 
ON  THE  PHYSIOLOGICAL  EXHAUSTION  AND  THE  VITAL- 
ITY OF  BEER  YEAST. 
By  M.  A.  Bechamp. 
The  life  of  the  leaven  being  contained  in  the  cellule,  I  sup- 
posed that,  so  long  as  this  cellule  was  neither  destroyed  nor  dead, 
the  leaven  would  continue  to  live,  and  to  manifest  this  life  by  its 
characteristic  chemical  actions,  but  in  certain  cases,  such  as  those 
about  to  be  described,  like  an  animal  in  a  state  of  inanition — that 
u  to  say,  in  exhausting  itself. 
To  measure  the  physiological  exhaustion  of  beer  yeast,  I  esti- 
mated the  phosphoric  acid  it  eliminates  while  consuming  its  own 
tissues,  when  forced  to  live  in  distilled  water. 
Mitscherlich  analyzed  beer  yeast,  and  from  his  analysis  con- 
f  See  Boussingault  "  Sur  le  Pulqua:"  report  made  to  the  Imperial 
Commission  for  Mexico. 
11 
