AmMa?;'i£)h7arm-}       The  Structure  of  the  Starch  Grain.  227 
lamellae  occurring  near  the  middle  of  the  grain ;  the  grain  mean- 
while swells  quite  perceptibly,  the  centre  becomes  clearer  {Jig.  14), 
the  contents  are  crowded  into  crescent-shaped  halves  which  are  still 
slightly  connected  at  the  poles  {figs.  13-if) ;  the  contents  of  each 
of  the  halves  of  the  grain  consist  of  crystalloidal  lamellae  in  which 
are  then  produced  small  clefts  or  channels  connecting  the  contigu- 
ous lamellae  {fig.  17)',  the  halves  in  some  instances  finally  separate 
and  slowly  dissolve  (figs.  18-20).  In  some  cases,  on  the  other 
hand,  there  is  a  corrosion  of  the  grain  at  the  periphery,  followed  by 
gradual  disintegration  without  the  separation  into  halves  (figs. 
21 ,  22). 
The  first  effect  of  reagents  upon  the  corn  starch  grain  {figs, 
23-34)  is  to  bring  out  the  point  of  origin  of  growth  {fig.  23),  the 
latter  becomes  larger  and  in  some  cases  more  or  less  zigzag  {fig.  23) 
in  outline ;  between  this  and  the  periphery  of  the  grain  arise  more 
or  less  interrupted  or  continuous  radial  channels  (usually  the  latter); 
the  crystalloidal  structure  of  this  grain  develops  slowly  and  is  most 
pronounced  when  the  grain  has  swollen  to  two  or  three  times  its 
normal  size ;  at  this  stage  we  find  that  the  centre  of  the  grain  has 
become  clear  and  the  point  of  origin  of  growth  has  become  oblit- 
erated in  some  cases  {fig.  24),  and  between  it  and  the  periphery 
occur  numerous  crystalloidal  lamellae  similar  to  those  observed  in 
the  potato  starch  ;  finally  the  peripheral  layer  ruptures  and  there  is 
gradual  disintegration  of  the  grain  (figs.  26, 30, 33).  Sometimes 
the  grain  appears  to  separate  into  as  many  parts  as  there  were  arms 
to  the  point  of  origin  of  growth  {figs.  2J,  28,34),  particularly  when 
acted  upon  by  saliva  or  diastase. 
A  number  of  authors  since  the  time  of  Nageli  have  shown  that 
the  lamellae  of  starch  grains  differ  in  constitution  and  structure,  and 
that  there  are  at  least  two  distinct  kinds  of  lamellae.  This  view  is 
confirmed  not  only  by  a  microphysical  examination  of  the  grain, 
and  by  treatment  with  weak  solutions  of  iodine  and  aniline  stains, 
but  also  by  treatment  with  water  and  various  reagents  as  just 
pointed  out.  Both  Salter  and  Meyer  appear  to  hold  to  the  theory 
that  there  is  a  distribution  of  crystalloidal  substance  in  particular 
lamellae.  Salter  quotes  Meyer  as  saying:  "  die  schattierten  Schich- 
ten  bedeuten  die  schwach  lichtbrechenden,  relativ  lockeren,  an  fester 
Substanz  relativ  armen,  an  Interstitien  reichen  Schichten,  die  hellen 
sind  als  die   stark  lichtbrechenden   Schichten  aufzufassen,  welche 
