514 
ON  NEW  ENGLAND  ISINGLASS. 
various  fishes,  some  only  of  which  have  been  hitherto  ascertained. 
The  finest  kinds  are  obtained  from  various  species  of  the  Acipen- 
ser,  but  fish  from  other  genera,  viz.,  Gadus,  Morrhua  and  others 
also  yield  it. 
The  organ  from  which  the  isinglass  is  usually  procured  is  the 
air  bag  or  swimming  bladder,  sometimes  termed  the  "sound." 
This  is  a  membranous  sac  filled  with  air,  (containing  from  69 
to  87  per  cent,  of  oxygen)  placed  under  the  spine  in  the  middle 
of  the  back,  above  the  centre  of  gravity.  In  most  fish  this  sack 
communicates  with  the  oesophagus  or  stomach  by  the  «  ductus 
pneumaticus  in  others  it  is  an  imperforate  sac,  and  occasionally 
there  are  two  sacs  which  communicate  with  each  other. 
As  long  ago  as  the  year  1772  the  manufacture  of  isinglass 
from  fish  was  considered  of  enough  importance,  by  Mr.  Humphrey 
Jackson,  of  England,  to  become  the  subject  of  careful  study; 
failing  in  his  endeavors  to  ascertain  in  England  the  process  fol- 
lowed, he  took  a  journey  into  Russia  for  the  purpose  of  arriving 
at  the  true  mode  of  manufacture. 
In  his  paper,  published  in  vol.  lxiii.  of  Phil.  Transactions,  he 
says  all  authors  who  have  hitherto  described  processes  for  mak- 
ing ichthyocolla,  have  greatly  mistaken  both  its  constituent 
matters  and  preparation,  and  cites  in  support  of  this  assertion 
the  remarks  of  M.  Pomet  upon  this  subject. 
The  latter  author  says,  as  to  the  manner  of  making  the  isin- 
glass :  "  The  sinewy  parts  of  the  fish  are  boiled  in  water  until 
all  dissolve  that  will ;  the  gluey  liquor  is  strained  and  cooled; 
after  cooling,  the  fatty  portion  is  removed  carefully  from  the 
surface,  the  liquor  itself  boiled  down  to  a  proper  consistency  and 
cooled,  cut  in  pieces,  twisted  into  crescent  shape  and  carefully 
dried  upon  sticks. 
From  this  we  could  reasonably  infer  that  all  fish  containing 
gelatinous  matter  could  be  used  with  advantage  for  the  manufac- 
ture of  this  article,  but  the  inference  would  be  an  erroneous 
one. 
The  sounds  or  bladders  of  fresh  water  fish  in  general  are  pre- 
ferred for  making  the  best  and  most  delicate  isinglass,  but  the 
article  known  in  commerce  as  "American"  is  made  from  the  air 
vessels  of  salt  water  fish. 
It  is  a  matter  worthy  consideration  whether  we  cannot  furnish 
