Particles  of  ftH>d  will  confuse  the  beginner.  L'mler  the  cover-glass
small  fragments  of  clastic  tissue  may  be  found  willi  the  low  power  of
the  microscope.  Larger  fragments  of  lung-tissue  arc  sometimes
present.  When  no  fragments  are  found  in  this  way.  a  search  with
the  higher  |)ower  mu.st  be  made  for  single  fibres  of  elastic  tissue,  in
which  ca.se  it  is  well  to  select  the  grayish  masses  of  sputum  from  the


THE   SPUTUM  31

tuberculous  cavity  or  the  particles  of  grass-green  or  slightly  rusty
sputa  which  are  present  in  a  subacute  caseous  pneumonia.  The  fresh
specimens  must  be  very  thin  ami  the  cover  well  pressed  down,  or  the
fibres  may  be  overlooked.
The  elastic  tissue  from  the  lung  may  be  present  in  three  arrange-
ments: most  important  is  the  alveolar  form,  in  which  case  the  fibres
preserve  the  outline  of  one  or  several  alveoli  (see  Figs.  4,  5),  and  the
fibres  are  long  and  branching;  from  the  bronchi,  in  which  case  the
fibres  are  single  or  in  small  groups,  fragmented  and  less  curled  than  in
the  former.  Dr.  Osier  considering  that  the  most  characteristic  picture
is  that  of  two  or  three  long  narrow  fibres  clustered  closely  together  in
an  elongated  net-work:  from  the  arteries  may  arise  a  distinct  sheet-
ing. Fragments  containing  a  coarse  net-work  of  short  interwoven
fibres  are  seen  from  ulcers  of  the  larynx.
When  the  elastic  tissue  is  very  small  in  amount  it  is  customary  to
destroy  all  other  tissue  by  means  of  jmtassium  hydrate,  but  if  the  above
Clark  method  be  carefully  used  this  method  is  not  necessary.  Ten
cc.  of  sputum  are  mixed  with  an  equal  amount  of  5  to  10  per  cent.
