132  Dose  Measures  and  Measured  Doses.  {Am^rch,S.rm' 
doses  is  increasing  to  such  an  extent,  that  an  inquiry  into  the  pos- 
sible variation  in  the  size  of  the  drops  was  thought  to  be  of  con- 
siderable and  timely  interest,  especially  in  view  of  the  fact  that  the 
Pharmacopceial  Revision  Committee  has  before  it  a  proposition  to 
adopt  an  official  or  standard  dropper. 
The  literature  on  the  subject  of  drops  is  quite  extensive.  The 
files  of  the  American  Journal  of  Pharmacy  alone  contain  numerous 
and  exhaustive  papers  on  this  subject,  and  many,  if  not  all,  text- 
books and  commentaries  have  considerable  amount  of  space  devoted 
to  a  more  or  less  exhaustive  review  of  the  subject,  and  also  the  more  " 
or  less  reliable  tables  of  the  number  of  drops  of  various  liquids  that 
are  necessary  to  measure  a  fluid  dram.  Many,  if  not  all  of  the 
investigations  that  are  usually  quoted,  were  carried  out  by  dropping 
either  from  the  lip  of  a  bottle,  the  edge  of  a  cork,  or  the  lip  of  a 
minim  graduate.  As  far  as  the  writer's  knowledge  goes,  no  exten- 
sive investigations  have  been  made  into  the  subject  of  drops  from 
the  much-used  medicine-dropper. 
In  dropping  liquids  from  a  pipette  it  is  essential  that  the  latter  be 
held  point  down,  if  correlating  results  are  to  be  obtained.  In 
actual  practice  this  necessary  precaution  does  not  appear  to  be 
recognized  or  appreciated.  In  some  experiments  that  were  made 
to  determine  what,  if  any,  effect  personal  equation  would  have  on 
the  number  of  drops  necessary  to  weigh  one  gramme,  it  was  noted 
that  comparatively  few  people  held  the  dropper  point  down,  but 
that  the  majority  held  the  pipette  at  such  an  angle  that  the  drop 
was  formed  from  the  side  rather  than  the  point  of  the  dropper. 
That  a  difference  in  the  way  a  pipette  is  held  has  a  most  decided 
effect  on  the  size  of  the  resulting  drop  is  well  illustrated  in  Table 
No.  7. 
Few  people  would  admit  that  there  could  be  such  a  variation  in 
the  size  of  drops  from  the  same  dropper,  but  a  series  of  experiments, 
that  any  one  can  conduct  for  himself,  will  be  the  best  way  of  con- 
vincing them  of  this  fact.  One  question  naturally  arises:  What 
dependence  can  be  placed  in  the  extensive  drop-tables  usually 
published  in  works  of  reference  ?  Here,  again,  the  answer  must  be 
with  the  individual,  and  the  only  suggestion  that  the  writer  wishes 
to  offer  is,  that  it  may  at  times  be  well  for  the  individual  to  try  and 
duplicate  some  of  the  quantities  stated  according  to  his  own  methods 
or  ideas. 
