1 
452    CONVERSION  OF  MANNITE  AND  GLYCERINE  INTO  SUGAR. 
out  putrefying  ;  if  it  putrefies  the  experiment  is  a  failure.  The 
formation  of  moulds,  and  especially  of  Penicillum  glaucwn,  is 
also  injurious.  After  an  interval  of  from  a  single  week  to  three 
months,  it  is  usually  found  that  a  substance  has  made  its  appear- 
ance capable  of  reducing  potassio-tartrate  of  copper,  and  fer- 
menting immediately  with  yeast.  At  this  moment  the  frag- 
ments of  testicle  are  separated  by  decantation,  and  completely 
freed  from  the  mannite  of  glycerine  by  repeated  washing ;  in 
this  state  they  possess  the  property  of  converting  these  two  sub- 
stances into  true  sugar.  The  prepared  tissues  are  operated 
with  in  the  way  just  described,  and  it  is  even  sufficient  to  im- 
pregnate the  tissue  with  a  solution  of  mannite  or  glycerine,  to 
obtain  a  very  abundant  formation  of  sugar  in  a  few  weeks. 
Some  experiments  made  with  dulcine  gave  similar  results. 
The  sugar  thus  formed  is  analogous  to  glucose  in  most  of  its 
properties.  It  could  not  be  obtained  crystallized,  and  is  very 
soluble  in  water,  aqueous  alcohol  and  glycerine,  from  which  it 
can  hardly  be  separated.  It  is  a  very  hygrometric  body,  very 
alterable  during  the  evaporation  of  its  solutions,  capable  of 
becoming  brown  under  the  influence  of  alkalies,  and  of  reducing 
potassio-tartrate  of  copper  ;  ammoniacal  acetate  of  lead  does 
not  precipitate  it  in  sensible  proportions.  With  yeast  it  ferments 
immediately,  producing  alcohol  and  carbonic  acid.  It  was  diffi- 
cult to  ascertain  whether  it  possess  a  rotatory  power,  from  the 
readiness  with  which  it  becomes  colored  during  the  concentration 
of  its  solutions.  Once  the  author  succeeded  in  observing  a 
deviation  of  the  tint  of  passage  equal  to  5° -5  for  a  length  of  200 
millims.  :  with  a  liquid  containing  about  one-twentieth  of  sugar ; 
it  would  therefore  have  a  left-handed  rotation,  and  be  distinct 
from  glucose  and  most  of  the  other  sugars  in  the  direction  of  its 
rotatory  power. 
One  of  the  most  decisive  of  the  author's  experiments  to  deter- 
mine the  origin  of  this  substance  and  the  influence  of  the  testi- 
cular tissue  upon  its  formation,  is  as  follows : — 
On  the  18th  of  December,  1856,  he  weighed  2  grammes  of 
fresh  cock's  testicle  (representing  0.280  grm.  in  the  dry  state), 
5  grms.  of  mannite,  and  50  grms.  of  water ;  the  whole  was  pat 
into  a  bottle  communicating  with  the  atmosphere  through  a  tube 
filled  with  carded  cotton,  and  left  in  a  moderately  heated  labor- 
