Ill 
ducts  of  Bertini,  the  largest  collecting  tubules,  contained  dark  reddish 
brown  granular  plugs  40/1  to  80/1  in  transverse  measurement,  similar 
to  those  already  described  in  the  urine  (Fig.  32),  and  giving  rise  to 
the  brown  radiation,  already  mentioned,  visible  to  the  naked  eye 
0  iX  rQ 
I'lG.  36.  Section  o£  medulla  of  kidney  during  suppression  of  urine,  eight 
days  after  haeraoglobinuria  had  ceased.  Blackwater  Fever,  Case  7a. 
A  collecting  tubule  is  shown  in  transverse  section.  The  lumen  of  the 
tubule  is  partly  filled  with  free  epithelial  cells  and  irregular  masses 
composed  of  darkly  stained  granules  of  varying  size,  which  have  for 
the  most  part  coalesced.  The  size  of  the  individual  granules  ranges 
from  3/i  to  5/i.  Some  of  the  free  epithelial  cells  contained  within  the 
tubule  exhibit  a  well  .stained  micleiis.  the  cytoplasm  of  the  cell  not 
being  markedly  altered  in  appearance;  in  others  the  cytoplasm  is 
stained  more  darkly  than  usual  and  the  nuclei  are  indistinct. 
Hardened  in  alcohol.  Stained  with  iron  alum  haematoxylin,  x  1150. 
in  the  medulla  of  the  kidney.  In  places  these  plugs  had  been 
detached,  sometimes,  but  not  always,  together  with  the  epithelial 
lining  of  the  collecting  tubule,  the  basement  membrane  being  then 
bare.  In  some  cases  a  granular  plug,  covered  externally  with 
