592  Central  {Axial)  Illumination.  {^d^S^' 
L  Union  Pharinaceutique  (quoted  in  the  National  Druggist,  Vol. 
xxi,  p.  162),  who  records  a  case  of  gouty  rheumatism,  in  which  he 
had  examined  the  urine  of  the  patient  before,  during  and  after 
treatment,  and  determined  a  very  decidedly  favorable  action  of 
lithium  salt  in  the  excretion  of  uric  acid. 
The  four  experiments  of  Gorsky  ought  to  be  mentioned  also, 
which  he  carried  out  in  the  year  1889,  at  the  laboratory  of  Loersch 
at  St.  Petersburg,  on  healthy  men,  each  lasting  twenty-four  days,  and 
by  which  he  arrived  at  the  conclusion  that  "  carbonate  of  lithia 
administered  in  gradually  ascending  doses,  from  two  to  eight  grains 
a  day  with  an  effervescent  water,  increased  the  daily  amount  of 
urine  and  with  it  the  daily  amount  of  the  excretion  of  uric  acid;" 
and  he  continues,  "  it  is  very  probable  that  lithia  favors  the  trans- 
formation of  uric  acid  into  urea,  and,  hence,  by  freeing  the  system 
from  the  acid,  promotes  a  more  energetic  cellular  action."  It  would, 
therefore,  seem  that  the  usefulness  of  lithium  salts  as  a  therapeutic 
agent  had  not  yet  outlived  itself ;  but,  on  the  contrary,  that  the 
salts  will  long  continue  to  be  employed  as  a  great  alleviator  of 
human  suffering. 
CENTRAL  (AXIAL)  ILLUMINATION.— 
By  Hans  M.  Wilder. 
It  will  probably  surprise  the  average  microscopist  to  learn  that 
Tie  very  likely  never  has  used  strictly  central  light.  One  should 
think  that  by  keeping  the  mirror-bar  accurately  in  line  with  the 
body-tube,  and  having  the  field  evenly  lighted,  the  illumination 
must  necessarily  be  central.  Jt  is  so  after  a  fashion,  but  in  most 
cases  the  illumination  is  as  much  as  5  to  10  degrees  out  of  centre. 
S.  Gage,  in  his  admirable  "  Microscopical  Methods,  "  recommends 
to  beat  thin  mucilage  until  milky,  transfer  a  little  to  the  slide,  and 
put  on  a  cover-glass,  without  pressing  it  down.  Search  the  prep- 
aration until  an  air  bubble  is  found  of  an  apparent  diameter  of 
one  Mm.,  get  it  in  the  centre  of  the  field,  and  apply  the  plane 
mirror.  If  cenlial,  the  bright  spot  will  be  found  exactly  in  the 
centre  of  a  dark  circular  ring  ;  if  not,  then  adjust  the  mirror  until 
it  is. 
I  think  that  the  following  method  will  be  found  easier  of  execu- 
tion :  Whatever  the  object  under  the  microscope,  select  a  spot  in  the 
