316  MR.  R.  OWEN'S  DESCRIPTION  OF  A  MICROSCOPIC  ENTOZOON 
from  one  another  ;  but  sometimes  a  larger  and  a  smaller  cyst  are  seen  attached  together 
bv  one  of  their  extremities,  and  they  are  occasionally  observed  slightly  overlapping  each 
other.  If  a  thin  portion  of  muscle  be  dried  and  placed  in  Canada  balsam,  between  a 
plate  of  glass  and  a  plate  of  talc,  the  cysts  become  more  transparent,  and  allow  of  the 
contained  coiled-up  worm  being  more  plainly  seen. 
Under  a  lens  of  the  focus  of  half  an  inch  the  worm  appears  to  be  inclosed  within  a 
circumscribed  space  of  a  less  elongated  and  more  regular  elliptical  form  than  the  external 
cyst,  as  if  within  a  smaller  cyst  contained  in  the  larger,  like  the  yolk  of  an  egg  sur- 
rounded by  its  albumen  and  shell.  The  worm  does  not  occupy  more  than  a  third  part 
of  the  inner  space.  A  few  of  these  cysts  have  been  seen  to  contain  two  distinct  worms; 
and  Dr.  A.  Farre,  who  has  paid  much  attention  to  the  subject,  has  shown  me  a  drawing 
which  he  made  of  one  of  the  cysts  containing  three  distinct  worms,  all  of  nearly  equal 
size. 
The  cysts  vary  in  form  as  well  as  size,  being  more  or  less  elongated,  and  the  opake 
extremities  being  further  extended  in  some  than  in  others  :  in  a  few  instances  only  one 
of  the  extremities  is  thus  produced.  Occasionally  the  tip  of  one  of  the  extremities 
is  observed  to  be  dilated  and  transparent,  as  though  a  portion  of  the  larger  cyst  were 
about  to  be  separated  by  a  process  of  gemmation ;  and  these  small  attached  cysts  are 
seen  of  different  sizes,  as  it  were,  in  different  stages  of  growth.  This  appearance, 
however,  I  conceive  to  be  explicable  without  a  reference  of  a  power  of  independent 
vitality  to  either  of  the  adherent  cysts. 
Besides  size  and  figure,  the  cysts  also  differ  in  structure  :  in  general  they  are  com- 
posed of  condensed  and  compacted  lamella  of  cellular  tissue,  but  a  few  are  hardened  by 
the  deposition  of  some  earthy  salts,  so  as  to  resist  the  knife,  and  to  break  with  a  gritty 
sensation  under  pressured 
In  order  to  detach  the  worm  from  the  cyst,  which  from  the  minuteness  of  the  object 
is  a  matter  of  some  difficulty,  I  have  found  it  best  to  select  a  portion  of  muscle  which 
has  been  placed  for  a  short  time  in  spirits  of  wine.  After  separating  the  cysts  from  the 
surrounding  fasciculi  of  muscle,  and  placing  them,  moistened  with  a  little  water,  on  a 
shp  of  glass,  I  have  generally  succeeded,  on  cutting  off  the  end  of  the  cyst,  or  tearing 
it  open  with  the  point  of  a  needle,  in  ejecting  the  worm  and  the  surrounding  fluid 
ill  which  it  floats,  by  gently  pressing  on  the  cyst. 
The  little  worm  is  usually  disposed  in  two  or  two-and-a-half  spiral  coils :  when 
straightened  it  measures  from  ^th  to  -g^th  of  an  inch  in  length,  and  from  ^wth  to 
T-Jpc-th  of  an  inch  in  diameter  :  a  high  magnifying  power  is  consequently  required  for 
its  examination.  It  is  cylindrical  and  fihform,  terminating  obtusely  at  both  extremities, 
which  are  of  unequal  sizes,  tapering  towards  one  end  for  about  a  fifth  part  of  its  length, 
'  This  change  is  probably  dependent  on  the  death  of  the  inclosed  worm,  the  traces  of  which  are  either  very 
obscure,  or  altogctlicr  wanting  in  these  ossified  cysts. 
