We hope 17:57, 12 Jan 2006 (UTC) The first insulin with any "length" to it was PZI in the 1930's, when Novo figured out how to add the protamine. Hagedorn, who worked for them, apparently began tinkering with this formula. He reduced the amount of protamine and came up with NPH. NPH came out in the '40's, Lentes not until the '50's.
Before the PZI, it was all beef R in varying U strengths and purity. Many shots a day.
Kathy