120  Standardization  of  Digitalis  Bodies.  \Kmjjjl™l\xw™' 
The  guineapig  method  at  best  requires  an  entire  day,  and  Hale 
found  that  it  often  consumed  two  days  for  a  single  assay. 
The  methods  are  all  humane  hence  this  point  needs  no  comment. 
The  last  minor  matter  is  that  of  expense.  Frogs  are  the  cheapest 
of  the  animals  but  they  are  prone  to  die  from  epidemics  of  the  "red 
leg  disease,"  and  a  large  number  of  each  consignment  is  usually 
female,  and  most  of  these  are  rendered  useless  by  the  presence  of 
large  masses  of  eggs,  so  that  it  is  not  probable  that  an  assay  by 
these  animals  could  be  done  at  a  cost  of  less  than  50  to  75  cents.. 
Hale  found  that  the  guineapig  method  cost  from  $2  to  $5.50  per 
assay.  In  New  York  City  cats  cost  ten  cents  each,  but  in  other 
cities  and  towns  they  are  more  expensive,  some  reporting  that 
they  cost  as  much  as  guineapigs.  If  the  factor  of  cost  is  so  impor- 
tant it  would  certainly  be  quite  as  possible  for  the  large  manu- 
facturing houses  to  breed  cats  as  it  is  guineapigs,  and  probably  at 
considerably  less  cost  than  in  the  case  of  the  latter,  for  their  food 
is  cheaper  and  they  do  not  eat  so  much.  The  cat  method  was  origi- 
nally proposed  as  one  which  would  be  available  for  the  small 
manufacturer  or  the  retail  pharmacist  and  it  would  certainly  seem 
that  it  is  still  the  preferable  method  for  this  purpose  as  it  is  always 
a  simple  matter  to  secure  four  to  six  cats  at  a  small  cost  and  without 
much  trouble,  whereas  the  purchase  and  keeping  of  guineapigs  and 
frogs  is  expensive  and  troublesome,  and  the  care  of  both  of  these 
animals  requires  special  facilities.  Both  are  liable  to  destruction 
by  unavoidable  factors,  frogs  by  drying,  and  the  "red  leg  disease," 
guineapigs  by  improper  food,  exposure  to  draughts,  epidemic  dis- 
eases, and  one  instance  might  be  mentioned  when  a  large  number 
of  these  animals  were  killed  in  a  single  night  by  the  invasion  of  a 
common  rat. 
SUMMARY. 
1.  The  frog  methods  are  the  cheapest  of  all. 
2.  The  one  hour  frog  method  and  the  cat  method  require  about 
the  same  length  of  time  and  are  much  less  time  consuming  than  the 
guineapig  or  twelve-hour  frog  methods. 
3.  All  four  methods  are  humane,  there  being  no  preference  on 
this  point. 
4.  The  guineapig  method  is  by  far  the  simplest,  both  of  the  frog 
methods  and  the  cat  assays  requiring  some  experience  and  skill. 
5.  All  of  the  methods  test  the  cardiac  action  of  the  specimen, 
but,  other  things  being  equal,  those  on  the  higher  animals  are  to 
