Am.  Jour.  Pharm. 
October,  1920. 
Urinary  Casts. 
717 
The  diameter  of  the  different  types  of  casts  show  a  characteristic 
uniformity.  The  sides  are  usually  parallel,  while  at  the  two  extremi- 
ties one  is  either  pointed  or  rounded,  and  the  other  is  frequently 
broken  across.  The  structure  may  otherwise  be  straight  or  con- 
voluted, while  the  length  varies  considerably. 
Though  it  is  difficult  at  times  to  distinguish  between  the  differ- 
ent varieties,  casts  have  been  classified,  according  to  their  micro- 
scopical characteristics  as  follows:  hyaline  casts;  waxy  or  colloid 
casts;  granular  casts  (fine  and  coarse);  epithelial  casts;  fatty  casts; 
blood  casts;  pigment  casts;  leukocyte,  pus  or  purulent  casts;  fibrinous 
casts;  bacterial  casts;  calcareous  casts;  ammonium  urate  casts; 
spermatic  casts. 
The  source  of  the  albuminous  material,  making  up  the  composi- 
tion of  a  cast,  is  not  known.  Some  claim  that  they  are  the  products 
from  broken  down  epithelial  cells,  contrary  to  the  belief  of  others, 
who  think  that  they  are  abnormal  secretions  thrown  off  by  diseased 
renal  cells.  Other  investigators  have  formed  the  opinion  that  the 
blood  plays  an  as  yet  unknown  r61e  in  the  production  of  these  patho- 
logical substances. 
Though  their  source  is  still  in  doubt,  it  is,  however,  the  belief  of 
most  workers,  that  this  albuminous  product  enters  the  uriniferous 
tubules  in  such  a  physical  state,  as  to  be  capable  of  being  easily 
molded.  It  is  also  held  that  they  are  formed  in  the  straight  tubules, 
and  not  in  the  convoluted  tubes.  The  casts  assume  the  shape  of 
the  tubule,  retaining  within  their  structure  whatever  substances 
were  lying  free,  and  then  bend  themselves  up,  or  are  forced  to  assume 
a  wavy  or  convoluted  shape,  due  to  the  obstacles  they  meet  as  they 
are  forced  out  by  the  pressure  of  the  urine.  It  is  for  this  reason 
that  the  various  forms  are  met  with.  There  apparently  seems  to 
be  no  definite  relationship  between  the  number  of  casts  present  and 
the  severity  of  a  morbid  process. 
Hyaline  Casts. — These  are  the  most  frequently  observed  casts, 
found  in  almost  all  kidney  disorders,  and  occasionally  in  transitory 
conditions.  They  are  straight  or  convoluted,  transparent,  homo- 
geneous, and  very  delicate  in  structure.  Their  length  and  breadth 
vary,  while  their  form  may  show  marked  variations.  These  casts 
are  frequently  coated  more  or  less  completely  with  albuminous 
debris  or  other  granular  material,  such  deposits  giving  a  granular 
appearance  to  the  casts.  The  impregnations  commonly  observed 
are  various  cells,  either  epithelium,  erythrocytes,  leukocytes  or  the 
