Between  this  group  and  the  next  is  a  very  large  group  of  casts,
the  commonest  form  in  some  cases  of  nephritis,  which  have  not  the
physical  properties  of  wax,  yet  are  more  distinct  and  solid-looking
than  the  hyaline,  which  name  they  bear.  It  is  important  to  recognize
that  some  of  these  have  deposited  on  them  fine  granules  from  the
urine,  giving  them  the  appearance  of  the  finely  granular  casts.  Their
chief  diflference  from  waxy  casts  is  that  they  are  not  so  solid-looking
and  do  not  give  the  same  color  tests.
Hyaline  Casts,  Colloid  or  Glassy  Casts  (see  Fig.  51). — These
are  pale,  very  little  refractive,  watery  in  appearance,  and  difficult  to
see  unless  the  light  is  almost  shut  oflf,  or  unless  crystals  or  cells  are
attached  to  them.  It  is  advised  to  stain  them  with  Lugol's,  giving  them
a  yellow  color,  or  aniline-violet,  giving  blue.  They  give  the  micro-
chemical  tests  for  albumin.  They  may  have  the  same  cells  attached
as  the  above  mentioned  casts.  Their  outline  is  very  regular.  These
casts,  which  occur  in  circulatory  disturbances  where  there  is  no  ques-
tion of  inflammation,  are  so  different  in  appearance  from  the  hyaline
casts  just  mentioned  that  they  deserve  a  separate  name.  They  are
soluble  in  acetic  acid.
Blood-Casts  (see  Fig.  52). — ^Blood-casts  are  coagula  of  red
blood-cells  which  have  formed  wnthin  the  tubules.  The  term  is  also
applied  to  any  of  the  above  casts  with  red  blood-cells  attached.  Some
of  the  blood-cells  are  so  pale  that  it  is  hard  to  recognize  them.
HEMOGLOBIN. — Casts  of  haemoglobin  are  seen  in  hsemoglobinuria,
the  haemoglobin  occurring  in  amorphous  masses.  Some  seem  like
other  casts  impregnated  with  haemoglobin.
