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Investigations conducted by Banting, Best, and Collip at the University of Toronto proved that it is possible to obtain a potent substance or extract, containing in concentrated form the secretion or hormone from the ductless portion of the pancreatic glands of mammalia, and cartilaginous fishes and the related glands (principal islets) of boney fishes, sufficiently free from injurious substances for repeated administration to human patients and having the physiological characteristics of removing the cardinal objective symptoms of diabetes mellitus in patients and reducing the blood sugar in laboratory animals.

The methods employed during these investigations involved the use of such reagents as ethyl alcohol, methyl alcohol, methylated spirits, and acetone, for extracting the secretion or hormone from the gland and then fractionally precipitating the potent substance free from the associated gland tissue and the injurious substances in the extractive solution.

From the results of our experience during these investigations we concluded that it is possible to extract the secretion or hormone from the gland by various reagents which tend to retard or inhibit the digestive action of the gland tissue and remove the injurious substances going into the extractive solution, and that it is also possible to concentrate and purify the potent substance in the extractive solution by the use of reagents which will unite with it as by absorption or by the use of reagents which will precipitate it free from adherent and associated substances. As extracting reagents we found that boiling water produced satisfactory results both in regard to the maximum yield of the potent substance and the small amount of proteins and other gland substances in the extractive solution and that