The First Steps With Insulin
Insulin was good, but it had to be made better. Other scientists stepped into the picture. John Abel, a Johns Hopkins University chemist, was the first to bring out pure insulin in crystalline form. This gave scientists a better chance to study the newly discovered hormone.
For diabetics, perfectly pure insulin was no blessing. It did not perform at top capacity unless traces of zinc were with it. So the zinc which had been distilled out of the crystalline insulin was put back in.
The pilot insulin had no measurement of strength. Since it soon became essential to know the concentration being employed, an arbitrary measurement was attained and called a unit. This was the quantity of insulin activity that could lower the blood-sugar of a rabbit by a particular amount. This measurement unit is still in use.
When the first commercial insulin came out, it was rather weak, providing 10 units of insulin activity per cubic centimeter. Then a more concentrated form of 20 units per cc. came along. These weak dilutions were wasteful to market and impractical for the patient. Today's concentrations of 40 and 80 units per cc. Give a better range for just about every patient, with one injection enough for a daily dose.
In 1927, five years after Joe Gilchrist got his first injection, there were two standard types of insulin available for diabetes patients—the original regular insulin and the newer crystalline zinc insulin. Both were clear liquids which were quickly absorbed and started to act within the hour. The effects held up for three or four hours then dwindled down quickly. This produced a problem. The action was of such short course that these insulin types must be injected before each meal and, by most patients, prior to going to bed. So the scientists went to work to cut down the number of daily injections.
For almost a decade, all sorts of experiments were done in the hope of discovering a way to prolong the action of insulin. Different kinds of materials were mixed with insulin in order to help slow it down, like paraffin, tannic acid, and alum.