260 Aqueous Extracts of Pancreas. I
leod that the atrophied pancress had been employed, was known
to us until their first paper (19), delayed in reaching our labora.
tory, was received in April, 1922. On the 27th of May, 1922, Dr.
Banting paid a visit to Rochester and from personal conversation
it was learned in just what manner acidulated alcohol had been
used by them in the preparation of extracts of whole pancreas.
Extracts of Pancreas of Foreign Species.
Up to this time no attempt had been made by us to prepare
extracts or perfusates for use with the human diabetic. But
encouraged by the report of Banting and Best and their colleagues,
we now began at once to study methods (24) of extraction and
purification with a view to the practicability of their use for the
relief of the human disease. Obviously, the packing house
products would become the major dependence as a source of
insulin. We, therefore, began parallel studies of extracts and
perfusates (25) of the pancreas of the pig and the steer. Banting
and Best seemed to have obtained their best results from alcoholic
extracts. We naturally wished to compare this method both
for potency and toxicity with the acid aqueous extracts which had
already yielded promising results.
Our first efforts to obtain potent but non-toxic extracts from
fresh slaughter-house material were not successful because the
exact reaction at which the proteins are precipitated upon neutrali-
zation seems to be different for the pancreas of different species.
After a few weeks, however, this point in the technique was
mastered so that water-clear filtrates containing very little protein
but containing, if not all, at least a very substantial fraction of the
antidiabetic potency could be prepared quite rapidly. They
were administered to completely depancreatized dogs in a variety
of ways, four of'which are illustrated in Tables III and IV and
Chart 1. Two dogs (Nos. 1 and 2) were studied simultaneously.
The extracts were given unconcentrated and without removal of
the salt resulting from neutralization of the acid used in extrac-
tion. The member of our laboratory team who had the best
mastery of the air analysis having been obliged to withdraw on ac-
count of illness, and while another was being trained especially for
thiswork, the respiratory quotient was neglected and attention was
concentrated upon the criteria of blood sugar and the D:N ratio.