70 SCIENTIFIC PROCEEDINGS (125)
Propertiea.ncd methods of preparation of the anti-diabetic sub-
stance (glucopyron) generated by the pancreas.
By JOHN R. MURLIN.
[Prom the Physiological Laboratory of the University of Roches-
ter, Rochester, N. Y.]
Repetition of several older methods of extraction of pan-
creas proved that with very slight modification any one of them
was adequate to demonstrate the presence of the anti-diabetic
substance. The essential steps in its preparation are: (1) de-
struction of trypsin; (2) precipitation of extraneous proteins;
(3) concentration; and (4) removal of irritant substances.
Banting1 and Macleod2 appear to have adopted exclusively the
method of alcoholic extraction and have given the name insulin.
to the alcoholic extract. Just as potent and non-toxic extracts
may be prepared with aquèous media. The active substance is
not all in the final precipitate with absolute alcohol as stated by
Collip3. It is non-dialyzable through vegetable parchment in four
hours' immersion in running water; it is not precipitated by most
of the ordinary reaeents employed for the precipitation of pro-
teins. It withstands boiling for 5 minutes in acid (N/10) media;
and it may be adsorbed on several differeng reagents commonly
used for this purpose.
Proof that an aaueous extract given with small amount of
alkali (N/20 NaOH) by stomach tube will cause oxidation of
su.rar in the depancreatized dog was given by Kramer4 and the
writer in 1916. For the active substance itself (not the entire
alcoholic extract) however obtained and whatever its chemical
nature the name Glucopyron (Glykos, sugar and Pyron, burning)
x Banting and Best, Journ. of Lab. and Oin. Med., 1922, vii, 464.
2 Macleod et al., lmer. Journ. of Physiol., 1922, lxii, 162.
g Collip, J. B., Trans. Roy. Soc. of Canada, 1922, xvi.
4 Murlin and Kramer, Journ. ot Biol. Chms., 916, vii, 516.