A  jannarryfi905rm'}  Pharmaceutical  Meeting.  47 
observation.  To  exclude  as  hearsay  that  which  is  based  upon  read- 
ing— even  when  it  can  be  discriminated — might  exclude  testimony 
as  to  the  homicidal  and  suicidal  tendencies  of  maniacs  if  one  had 
never  actually  seen  a  maniacal  killing,  as  well  as  testimony  as  to  the 
possibility  of  death  from  strychnin,  if  one  had  never  actually  seen  a 
person  die  from  such  cause,  or  as  to  the  presence  of  arsenic  in  a 
normal  thyroid  gland  if  one  had  not  made  a  personal  analysis. 
Expert  witnesses  concerning  pharmacologic  questions  are  called 
upon  to  give  four  different  orders  of  testimony  not  usually  discrimi- 
nated. They  are  all  treated  as  matters  of  opinion,  but  in  reality 
three  relate  to  matters  of  fact.  (1)  Personal  observations  on  the 
part  of  the  witness  as  to  the  effect  of  drugs  on  the  human  or  animal 
body  are  judgments  of  fact.  They  may  be  mistaken  judgments,  as 
may  also  be  the  judgment  of  a  surveyor  as  to  the  location  or  dimen- 
sion of  a  certain  plot  of  ground,  but  both  judgments  are  of  the  same 
order  ;  they  both  depend  on  the  interpretation  of  data  observed  by 
special  methods.  They  differ  from  ordinary  judgments  of  fact  and 
from  each  other,  not  in  kind,  but  in  degree  of  complexity.  (2)  The 
methods  ot  chemical  analysis  and  their  results  are  obviously  matters 
of  fact.  The  conclusions  based  thereon  are  judgments  of  fact  as  in 
the  case  first  cited.  That  arsenic  has  or  has  not  been  found  in  a 
given  case  is  not  a  matter  of  opinion,  but  one  of  fact.  It  is  to  be 
criticised  lrom  that  standpoint.  If  the  methods  pursued  have  been 
faulty,  or  if  the  results  have  been  inconclusive,  that  can  properly  be 
shown,  but  also  as  matters  of  fact.  (3)  Matters  of  general  scientific 
knowledge,  e.g.,  as  to  the  action  of  drugs,  or  the  contamination  of 
foods,  drugs  and  manufactured  articles  of  various  kinds  by  poisons, 
or  as  to  chemical  and  pharmaceutic  incompatibilities,  and  so  forth, 
are  also  matters  of  fact,  whether  within  or  without  the  personal 
observation  of  the  witness.  Concerning  matters,  however,  which 
are  not  only  outside  the  observation  of  the  witness,  but  beyond  the 
usual  range  of  his  studies,  he  can  only  have  an  opinion.  He  cannot 
know  them  as  facts,  and  he  should  refuse  to  testify  concerning 
them.  (4)  When  the  witness  has  made  no  personal  observation, 
and  is  called  upon  to  form  judgment  upon  data  which  consist  of  the 
descriptions  and  judgments  of  others  bearing  upon  a  particular  case, 
he  cannot  know  the  facts,  and  he  cannot  give  testimony;  he  can 
only  express  an  opinion.  The  fact  that  the  opinion  is  expressed 
in  court  and  under  oath  does  not  alter  its  character.    It  is  purely 
