♦ 
44       Drug  Sections  for  Microscopical  Examination.  {Am'j£nT/im*Tm' 
some  clove  oil  until  it  sinks  (usually  in  about  five  minutes) ;  it  will 
then  be  found  to  be  quite  clear,  and  is  ready  for  mounting  in  Canada 
balsam,  or  more  conveniently  a  mixture  of  Canada  balsam  and  one- 
fifth  its  bulk  of  pure  turpentine. 
The  brightness  of  a  section  stained  with  borax  carmine  is  increased 
by  placing  in  a  mixture  of  spirit  and  one-sixth  its  bulk  of  hydrochloric 
acid  for  a  minute  or  so.  The  acid  must  afterwards,  of  course,  be 
thoroughly  washed  out. 
If  a  section  is  overstained  it  may  be  remedied  by  placing  in  a  dilute 
spirituous  solution  of  hydrochloric  acid  or  dilute  aqueous  solution  of 
acetic  acid  according  to  the  stain  used. 
Double  staining  is  accomplished  by  using  alkaline  and  acid 
solutions  respectively ;  for  example,  green  and  red  by  first  plac- 
ing in  an  acid  green  solution,  washing  with  water,  and  then  plac- 
ing in  borax  carmine  solution,  then  wash  in  spirit  and  clear  in 
clove  oil. 
Clove  oil  is  a  very  good  clearing  medium  and  a  very  good  vehicle 
in  which  to  preserve  the  sections  until  required  for  mounting,  if  it  is 
intended  to  mount  them  in  Canada  balsam.  If  a  specimen  is  stained 
before  it  is  sectionized  it  must,  of  course,  be  left  in  the  stain  hours,  and 
perhaps  days,  instead  of  minutes  ;  this  is  only  done  with  soft  tissues, 
such  as  ovaries,  which  should  be  gathered  before  they  are  quite  ripe. 
Fresh  stems  should  not  be  more  than  three  years  old  as  a  general 
rule. 
Sections  must  not  be  bleached  where  there  are  cystolithes  or  any 
other  cell-contents  which  the  bleaching  fluid  would  dissolve.  Certain 
resinous  drugs,  such  as  pellitory,  must  not  be  mounted  in  Canada  bal- 
sam, which  would  dissolve  out  the  resin  ;  in  such  cases  glycerin  jelly 
containing  carbolic  acid,  arsenic,  or  some  other  preservative,  should  be 
used.  This  is  best  used,  not  with  a  rod,  but  filtered  while  hot,  and 
liquid  through  cotton  wool  directly  on  to  the  slide.  To  keep  glycerin 
in  is  a  very  difficult  matter.  Gold  size,  which  is  at  least  ten  years' 
old  and  quite  "  tacky,"  or  sticky,  is  a  very  good  cement,  but  it  should 
be  touched  over  about  every  five  years. 
Certain  black  cements  are  very  liable  to  run  into  the  Canada  balsam 
and  spoil  the  sections. 
In  conclusion,  I  would  reaffirm  that  it  is  cheaper  to  make  than  to 
buy  a  good  collection  of  drug  sections,  especially  as  many  are  only  ob- 
tainable on  the  continent. 
