The  methods  employed  for  producing  experimental  diabetes  in  investi-
gation of  these  problems  by  the  indirect  method  are  (1)  the  entire  removal
of  the  pancreas,  and  (2)  the  continuous  administration  of  the  drug
phlorhizin.  The  animal  rendered  diabetic  by  either  of  these  methods  is
first  of  all  observed  for  several  days  to  determine  the  normal  daily  ex-
cretion of  sugar.  At  the  same  time  the  nitrogen  excretion  for  the  day
is  determined,  the  ratio  between  the  total  nitrogen  and  the  glucose  being
known  as  G  to  N  ratio,  and  being  about  1  to  3.65  when  complete  diabetes
has  become  established.  The  foodstuff  in  question  is  then  fed  to  the
animal,  and  the  amount  of  extra  glucose  excreted  thereby  is  taken  to
represent  that  which  has  been  derived  from  the  ingested  food.  By  this
method  it  has  been  possible  to  show  that,  not  only  the  above  mentioned
carbohydrates,  but  protein  as  well  produce  a  very  considerable  quan-
tity of  glucose  in  the  animal  body.  Fats,  however,  yield  only  negative
results.
The  indirect  method  has  another  great  advantage  over  the  direct  in
that  the  results  are  much  more  quantitative  in  character;  for  example,
Lusk  and  his  pupils  have  been  able  to  determine  the  amount  of  glucose
which  can  be  produced  by  feeding  certain  of  the  building  stones  of  the
protein  molecule.  The  great  practical  importance  of  such  results  in


THE   METABOLISM  OP   THE   CARBOHYDRATES  665

the  therapy  of  diabetes  makes  it  advisable  for  us  to  go  into  the  subject
a  little  more  in  detail  here.
