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free from injurious substances including inert associated gland tissue, proteins, proteclytic enzymes, slats and lipoids.
The following are steps we employed in several methods for obtaining a practically pure extract from the fresh pancreas of mammalia:
(1) Separation of the internal secretion or hormone from the fresh pancreas by extraction with solvents such as ethyl alcohol, methyl alcohol, methylated spirits, and acetone, or any mixture of these, which are capable of preserving the activity of this internal secretion or hormone by not destroying it and by largely preventing or inhibiting the deleterious action on it of such proteclytic enzymes as trypsin, erepsin, and the proteases, and of other catalysts present, followed by filtration for the removal of the inert associated gland tissue.
(2) Removal of the major part of the proteins by some suitable method of precipitation. For this purpose alcohol, colloidal iron, precipitation at isolectric point by the use of dilute acid or alkali, or heating to a suitable temperature, may be used.
(3) Concentration of the extracted filtered solution, either before or after the removal of the proteins, as by distillation in vacuo, or evaporation in a dry air current.
(4) Removal of the lipoids after concentration either by mechanical separation or by chemical extraction with solvents such as ether, or toluol.
(5) Removal of the salts and a large part of the remaining impurities by precipitation with alcohol.
(6) Precipitation of the internal secretion or