When Banting finally began his experiments in the summer of 1921, he quickly realized all the practical problems. His years as an army doctor left him a highly skilled surgeon. He could easily perform the surgery on the dogs, but he didn’t have good surgical facilities. He performed the surgeries in an old lab that Macleod made available to him. The first few dogs he operated on developed infections and died. Macleod was not available to help him that summer, since he had left for his summer holiday.
Despite the initial difficulties, Banting and Best soon found success. By the time Macleod returned from his summer holiday, Banting and Best had not only been able to surgically induce diabetes in a dog, as Minkowski had done three decades earlier, but also keep the dog alive by injecting extracts from another dog’s pancreas. The experiments had worked just as Banting had predicted.
When Macleod saw the results in the fall of 1921, he was impressed. He had never thought isolating insulin would be so easy. However, he asked Banting and Best to repeat their experiments. Repeating the experiments was a reasonable request for such an important finding, but Banting was not used to doing scientific experiments. He was insulted by the request and this incident was the beginning of ongoing tension between Macleod and Banting. Banting finally agreed to redo the experiments, on the condition that Macleod provide him with better facilities and a salary. He had worked all summer without pay, selling his house and medical instruments back in London to finance his experiments. The repeated experiments were also successful.