Insulin and Diabetes.
Insulin was Discovered by Banting and Best.
It had been known for some time that people with diabetes had a lot of sugar in their urine. In the 19th century, scientists removed pancreases from dogs, and the same sugary urine was observed. The dogs became diabetic. That suggested that the pancreas had something to do with the disease. In the 1920's Frederick Banting and his assistant Charles Best managed to successfully isolate insulin, the hormone that controls blood sugar levels.
1) Banting and Best tied string around a dog's pancreas so that a lot of the organ wasted away - but the bits that made the hormone were left intact.
2) They removed the pancreas from the dog, and obtained an extract from it.
3) They then injected this extract into a diabetic dog and observed the effects on their blood sugar levels.
4) They found that after that after the pancreatic extract was injected, the dogs blood sugar level fell dramatically. This shows that the pancreatic extract caused a temporary decrease in the blood sugar level.
5) They went on to isolate the substance in the pancreatic extract, insulin.