Abstract
Repetition of several older methods of extraction of pancreas 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) destruction of trypsin; (2) precipitation of extraneous proteins; (3) concentration; and (4) removal of irritant substances. Banting 1 and Macleod 2 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 aqueous media. The active substance is not all in the final precipitate with absolute alcohol as stated by Collip 3 . It is non-dialyzable through vegetable parchment in four hours' immersion in running water; it is not precipitated by most of the ordinary reagents employed for the precipitation of proteins. It withstands boiling for 5 minutes in acid (N/10) media; and it may be adsorbed on several different reagents commonly used for this purpose.
Proof that an aqueous extract given with small amount of alkali (N/20 NaOH) by stomach tube will cause oxidation of sugar in the depancreatized dog was given by Kramer 4 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) is suggested.
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