522  The  Microscope  in  Materia  Medica.    { ^oT^"* 
(2.)  Precipitate  20  grams  of  silver,  dissolved  in  60  grams  HN03  by 
an  aqueous  solution  of  20  grams  of  caustic,  potassa  place  on  a  filter, 
wash  with  water,  and  dissolve  on  the  filter  in  an  aqueous  solution  of 
100  grams  of  potassium  cyanide  ;  add  water  to  make  2  liters. 
Both  solutions  are  used  by  immersing  the  bright  metals  which  are  to 
be  plated  into  them. — Ibid.,  July  25,  p.  282,  from  Ibid. 
THE  MICROSCOPE  IN  MATERIA  MEDICA. 
By  Thomas  Greenish,  F.C.S. 
Vegetable  histology  is  a  subject  which  merits  more  attention  from 
the  pharmacist  than  it  usually  receives.  The  necessity  of  a  general 
knowledge  of  botany  or  the  natural  history  of  the  vegetable  kingdom 
is  fully  recognized,  but  the  pharmacist  in  dealing  with  the  vegetable 
materia  medica  requires  something  beyond  and  more  special  than  this 
general  knowledge.  He  should  know  the  organographic  locality  of 
the  active  constituents  of  the  different  plants  used  in  medicine  and  also 
something  of  the  histological  localization  or  the  particular  tissue  or 
tissues  in  which  those  active  principles  reside.  The  anatomy  of  these 
elementary  parts  of  which  the  organs  of  plants  are  composed  consti- 
tutes vegetable  histology,  and  the  several  cells  are  distinctly  visible 
and  capable  of  being  examined  and  identified  onlv  with  the  acid  of  the 
microscope. 
As  one  instance  in  point,  cinchona  bark  may  be  mentioned. 
Wigand  investigated  this  bark  with  a  view  of  determining  the  ques- 
tion which  had  occasioned  some  controversy,  which  of  the  cell  tissues 
was  the  seat  of  the  alkaloid  ?  Chiefly  through  the  employment  of 
reagents  he  came  to  the  conclusion  that  the  alkaloid  resided  mainly  in  the 
bast  or  liber  cells ;  but  the  more  careful  experiments  conducted  by 
Carl  MUller  have  settled  this  question  and  have  placed  beyond  doubt 
the  fact  that  the  parenchymatous  tissue  is  the  seat  of  the  alkaloid  in 
the  cinchona  bark,  and  this  opinion  has,  I  believe,  never  since  been 
called  into  question.  The  relative  proportions,  therefore,  of  bast  or 
liber  to  parenchymatous  tissue  in  a  given  sample  of  cinchona  bark,, 
which  to  a  certain  extent  may  be  indicated  by  its  short  or  otherwise 
fibrous  fracture,  is  an  element  of  some  practical  value  prior  to  a  chemi- 
cal analysis. 
Cultivation,  with  reference  to  particular  soils,  has  the  property  of 
