CONVERSION  OF  MANNITE  AND  GLYCERINE  INTO  SUGAR.  451 
of  carbonate  of  lime  and  caseine,  their  conversion  into  alcohol, 
either  at  104°  F.  or  at  50°  F.,  takes  place  directly,  without  the 
least  indication  at  any  moment  of  the  temporary  existence  of  a 
true  sugar.  But  the  regular  course  of  these  experiments  re- 
quires the  presence  of  carbonate  of  lime  ;  if  this  be  suppressed, 
the  mannite  and  glycerine  usually  remain  unaltered,  but  some- 
times, and  only  under  peculiar  circumstances,  the  formation  of 
a  true  sugar  may  be  observed. 
Mannite  and  glycerine  dissolved  in  water  were  left  at  the 
ordinary  temperature  in  contact  with  all  the  nitrogenous  tissues 
and  substances  of  an  animal  or  analogous  nature  which  the 
author  could  procure.  In  many  cases  a  true  sugar  was  pro- 
duced, capable  of  reducing  potassio-tartrate  of  copper, 
and  of  undergoing  alcoholic  fermentation  under  the  influence 
of  yeast. 
The  conditions  of  this  formation  of  sugar  are  sometimes  capable 
of  definition,  sometimes  exceptionable.  It  was  observed  with 
albumen,  caseine,*  fibrine,  gelatine,  and  cutaneous,  renal,  pan- 
creatic tissues,  &c,  but  always  accidentally,  and  so  that  the 
conditions  of  the  phenomenon  could  not  be  determined. 
The  tissue  of  the  testicle  alone  caused  the  conversion  of  gly- 
cerine and  mannite  into  true  sugar  almost  in  a  regular  manner. 
The  testicles  of  man  or  animals  (the  cock,  dog,  or  horse)  are  cut 
into  small  pieces  and  placed  in  a  solution  consisting  of  10  parts 
of  water  and  1  part  of  mannite  and  glycerine  ;  the  weight  of  the 
animal  tissue  (supposed  to  be  dry)  should  represent  about  ^-th 
of  the  mannite  or  glycerine.  The  operation  is  effected  in  an 
open  bottle,  under  the  influence  of  diffused  light,  at  a  tempera- 
ture between  50°  and  68°  F.    The  tissue  usuallv  remains  with- 
*  The  following  are  some  of  the  causes  of  error  which  must  be  well 
guarded  against  in  these  experiments  : — 1.  Albumen  and  caseine  contain 
small  quantities  of  sugar,  of  which  they  must  be  freed.  2.  The  mannite 
of  commerce  must  always  be  purified,  as  it  contains  1  to  2  per  cent,  of 
sugar.  This  sugar  is  derived  from  manna,  which  contains  10  to  15  per 
cent.  The  amount  of  sugar  pre-existing  in  manna  does  not  increase  by 
keeping.  Besides  sugar  and  mannite,  manna  contains  nearly  half  its 
weight  of  little  known  substances,  so  that  the  employment  of  manna  in 
these  experiments  cannot  lead  to  any  conclusion.  3.  The  so-called  puri- 
fied commercial  glycerine  contains  a  body  capable  of  reducing  tartrate  of 
copper. 
