INSULIN BY EXTRACTION 417
Relative amounts of insulin obtained by extraction and by
perfusion of the pancreas.
By H. D. CLOUCH and J. R. MURLIN.
[From the Physiological Laboratory of the University of Roch-
ester, Rochester, N. Y.]
We have employed two essentially different methods for ob-
taining insulin from the excised pancreas of various animals:
First, extraction with different media after maceration of the
pancreases; and secondly, perfusion of the intact organs with
various solutions. In a series of twenty-nine perfusions done
during the past ten months we have purposely varied the many
factors involved-such as the composition of the perfusion fluid,
the temperature of the chamber containing the organs, the rate
of perfusion, volume of perfusate, time of perfusion, and per-
fusion pressures-within wide limits in order to select fhe sim-
plest method which is efficient. A comparative analysis of these
various factors leads us to conclude that the simplest efficient
method is that of continuous gravity perfusion with 0.2 per cent.
HCI at or somewhat above body temperature (37C. to 45C.),
under a pressure of 120 mm. Hg, for a period of one hour.
In determining the potency of preparations we have used a
dose of two cubic centimeters of final concentrated product ad-
ministered subcutaneously to normal rabbits. Blood is taken
from the ear veins before the injection and again two hours after
the injection. A drop of 70 milligrams in blood sugar is taken
as a rabbit unit and on this basis the yield in rabbit units per kilo
of pancreas is calculated.
The perfusion method appears to give about three times as
much insulin (estimated as Rabbit Units) per kilo as is obtained
by the extraction methods employed and gives a product which
is much more easily and quickly concentrated because of the
absence of the large amounts of protein and extraneous material
which were obtained when extraction processes were used.