My first job after leaving school in 1968 was in the (new) insulin lab. I can only remember one name, Derek Wardle, who I bought my first motorbike from.
The insulin was extracted from the pancreas of cattle. The pancreas was ground up in a very large mincer and dropped down into a vat which I think contained absolute alcohol to dissolve the insulin out. There were a few stages of refinement. The concentrate came into the lab to be further refined and filtered.
Pigs gut was processed, in another building that I only visited once, to extract heparin I think. The guts