444 
ON  FERMENTATION. 
Cold  water  extracts  of  flour  and  malt  were  added  to  cane-sugar 
solution,  which  also  contained  some  glucose.  The  extract,  on 
addition  of  sugar-cane,  was  converted  into  mucilage;  and  the 
change  is  permanent  in  flour-extracts,  but  extracts  of  barley- 
meal  possess  great  power  to  produce  the  yeast-cells,  which  act 
upon  the  mucilage,  and  resolve  a  portion  of  it  into  alcohol  and 
carbonic  acid.  The  developement  of  the  yeast  cells  in  the  muci- 
lage is  a  most  interesting  sight :  the  cells,  as  they  multiply,  are 
prevented  from  separating,  on  account  of  the  thickness  of  the 
solution,  and  thus  remain  clustered  together. 
Cold  water  extracts  of  grain  abound  with  microscopic  para- 
sites, which  soon  set  up  a  strong  action,  thereby  giving  rise  to 
the  production  of  acid,  and  doubtless,  also,  to  the  transformation 
of  the  cane-sugar  into  mucilage.  Boiling  destroys  these  para- 
sites, prevents  in  a  great  measure  the  production  of  acid,  and 
subsequently  yields  more  alcohol.  This  conclusion  was  arrived 
at  after  many  and  varied  experiments. 
When  "pus"  was  employed  as  ferment,  a  fungoid  organism, 
similar  to  that  obtained  by  albumen  from  flour  and  malt,  was  de- 
veloped in  the  solution,  which  likewise  possessed  very  little  fer- 
mentative power. 
The  fermentative  properties  of  two  moulds,  the  blue  mould 
from  moist  malt,  and  the  mould  from  lemon-juice,  were  next  in- 
vestigated in  a  glucose  solution.    Both  proved  good  ferments. 
In  order  to  compare  the  relative  fermentative  power  of  the 
yeast-plants  of  malt  and  the  grape,  the  following  experiments 
were  instituted : — 
To  a  solution  capable  of  giving  16  per  cent,  alcohol,  brewers' 
pressed  yeast  was  added  successively.  The  limit  was  reached 
on  the  sixteenth  day ;  but  the  experiment  was  carried  on  for  up- 
wards of  thirty  days,  when  the  alcohol  in  the  liquid  amounted  to 
15.91  per  cent.  When  the  extreme  point  w^as  reached,  the  yeast- 
cells  became  contracted  and  shrivelled ;  but,  when  they  were 
transferred  to  a  fresh  sugar-solution,  they  recovered  their  vitality. 
In  several  cases,  glucose  was  added  to  the  cane-sugar  solution ; 
and  it  was  here  observed  that,  in  the  presence  of  an  excess  of 
glucose,  comparatively  less  alcohol  was  obtained  :  the  aleohol  and 
glucose  combined  seemed  to  act  as  an  antiseptic. 
