AmDe0cUri87h9arm }         Perimetric  Dimension  System.  593 
30  mm.  as  closely  approximating  the  dimensions  of  No.  18  of  the 
American  scale. 
A  comprehensive  plan  of  unification  is  thus  afforded,  based  upon 
the  best  known  standard ;  for,  whatever  may  be  the  faults  of  the 
metric  system  for  general  mechanical  purposes,  it  is  perfect  for  surgical 
uses.  Neither  can  objection  be  raised  to  it  in  this  case,  on  the  ground 
of  infraction  of  established  routine,  as  is  done  in  regard  to  its  introduc- 
tion into  medicine  and  pharmacy,  for  in  surgery  there  is  no  generally 
accepted  standard  to  be  displaced.  In  fact,  except  in  the  case  of  the 
urethral  instruments  before  mentioned,  there  has  been  no  attempt  to 
indicate  actual  dimensions  of  any  kind  in  the  numbering  of  surgical 
instruments  ;  while  the  sizes  of  nearly  all  appliances  in  use  are  purely 
arbitrary,  if  not  in  many  instances  simply  the  result  of  accident. 
Metric  terms  are  now  almost  universally  adopted  as  part  of  the 
language  of  general  science,  and  surgery  can  have  nothing  to  lose  but 
much  to  gain  by  the  acceptance  of  a  standard  so  truly  International. 
While  the  proposed  system  of  measurement  is  fixed  and  definite,  it 
yet  allows  entire  freedom  for  individual  choice  on  the  part  of  the  surgeon 
in  the  gradation  of  the  sizes  of  instruments,  both  as  regards  their  num- 
ber and  their  relative  dimensions.  It  includes  and  utilizes  all  scales,  by 
giving  them  a  common  nomenclature;  being  especially  in  accord  with 
the  French  urethral  scale,  however,  for  in  this— though  it  is  limited  to 
certain  fixed  gradations — nominal  number  and  actual  size  expressed  in 
metric  terms  correspond.1 
The  importance  of  measurement  by  circumference  or,  preferably,  by 
perimeter,  instead  of  by  diameter,  is  not  to  be  overlooked,  inasmuch  as 
many  instruments  are  irregular  in  outline,,  and  therefore  not  susceptible 
of  measurement  by  the  litter  method. 
The  Adaptable  Metric  Guage  supplies  a  ready  means  for  rendering 
the  foreg  >ing  plan  practicable,  and  thus  securing  the  highest  degree  of 
definitness  and  accuracy,  for  purposes  of  record,  comparison  and  opera- 
tive procedure.  In  illustration  :  during  several  years  I  have  made 
somewhat  frequent  use  of  Otis's  dilating  urethrotome  in  obstinate  and 
irritable  stricture,  and  though  using  at  different  times  the  best  procur- 
1  The  American  scale,  with  its  distinctive  gradations,  may  be  virtually  reproduced 
by  the  same  method  by  making  successive  advances  in  size  of  15  mm.  in  circum- 
ference— as  i,  2-5,  4,  5-5,  7  mm  ,  etc 
37 
