Am.  lour.  Pharm.  1 
Dec,  1879.  J 
Perimetric  Dimension  System. 
THE  PERIMETRIC  DIMENSION  SYSTEM  ; 
A  GENERAL  SYSTEM  OF  MEASUREMENT  FOR  URETHRAL, 
UTERINE,  RECTAL  AND  OTHER  INSTRUMENTS:  AND  AN 
ADAPTABLE  METRIC  GAUGE.1 
By  Charles  Hermon  Thomas,  M.  D.,  Fellow  of  the  College  of 
Physicians,  etc.  5  of  Philadelphia,  Pa. 
Three  scales  for  grading  and  numbering  urethral 
instruments  are  now  in  use  in  the  United  States,  each  scale 
having  distinct  characteristics.  The  differences  between 
them  are  radical  and  material,  and  they  are  not  accu- 
rately interconvertible.  Of  these  conflicting  standards 
the  universally  known  French  scale  is  doubtless  usually 
preferred,  and  indications  are  not  wanting  which  point  to 
its  general  adoption.  The  English  scale,  formerly 
almost  exclusively  used,  is  purely  arbitrary  in  character; 
has  proved  inaccurate  in  practice ;  is  inconveniently 
limited  in  its  range  of  sizes,  and  is  rapidly  falling  into 
disuse;  while  the  American  scale,  somewhat  re- 
cently introduced  —  though  undoubtedly  an  improve- 
ment on  the  English — is  at  least  lacking  in  simplicity, 
and  its  claim  to  supplant  the  French  has  yet  to  be 
justified. 
According  to  the  French  scale,  each  size  in  a  set  of 
catheters  or  bougies  is  derived  from,  and  identical  with, 
the  number  of  millimeters  in  circumference  which  such 
instrument  actually  measures — an  arrangement  at  once 
rational  and  simple.  Thus,  while  No.  I  is  I  mm.  in 
circumference,  No.  2  is  2  mm.,  No.  3,  3mm.,  and  soon 
uniformly  throughout. 
The  American  scale,  though  like  the  French  founded 
on  the  metric  system,  has  for  its  gradations  half  millime- 
ters in  diameter,  instead  of  whole  millimeters  in  cicum- 
ference.  Its  numbers,  however,  are  consecutive  in  units, 
and  therefore  correspond  neither  with  the  figures  which 
represent  diameters  nor  circumferences.  Practically  it 
differs  from  the  latter  in  that  it  does  away  with  one  in 
Exhibited  to  the  Philadelphia  County  Medical  Society,  June 
25th,  1879. 
