The first task that Banting and Best undertook when they arrived at the University of Toronto’s Medical Building early on May 17, 1921, was cleaning the physiology department’s animal operating room. 

Built in 1903, the Medical Building — located on King’s College Circle until the university replaced it with the Medical Sciences Building in 1969 — was designed to facilitate scientific research. But after several years of limited use during and following the First World War, the research labs definitely needed some spic and span. In fact, the initial part of Banting and Best’s research was to be conducted in a small room Banting felt “was not fit to be called an operating room.” Before Macleod joined them, they scrubbed the floor, washed the walls and windows and cleaned its wooden operating table (which, of course, could not be sterilized). 

The first part of the research plan was to operate on several dogs to remove their pancreases and trigger diabetes. Though an experienced surgeon, Banting had not done a pancreatectomy on a dog before. The procedure mainly involved cutting the pancreas away from the tissue (mesentery tissue) that attaches the intestines to the wall of the abdomen. The critical part was carefully ligating (tying off) the many blood vessels that supply the pancreas before cutting through them, otherwise bleeding could be uncontrollable. It was also important not to damage nearby blood vessels and organs. Macleod instructed him during the operation while Best assisted. This first step also provided Banting and Best an opportunity to observe the development of diabetes in the dogs while Best was able to practice blood sugar and urine testing.

Banting and Best quickly developed a good working relationship, although their backgrounds and temperaments were quite different. When Charles (“Charlie”) Herbert Best joined Banting, he was 22 and had just graduated with his Bachelor of Arts degree from U of T’s Honours Physiology and Biochemistry program. By all accounts, Charlie was strikingly handsome, tall, blonde, athletic and popular. He was born in Maine, the son of a small-town physician with deep family roots in Nova Scotia. Best moved with his family to Toronto in 1915, where he completed his high school education and then entered university. In 1918, he enlisted in the Canadian Army and had reached England as a sergeant in the artillery when the war ended. 

After the war, Best resumed his second year in the physiology and biochemistry course. He took full advantage of university and fraternity life, improving his marks during his final year to win second-class honours and impressing Macleod, who chose him as a demonstrator and then suggested he work with Banting.

On May 17th, the first pancreatectomy took about 80 minutes and the dog recovered. It was a two-step operation that left a small portion of the pancreas intact. A week later, they removed the remaining part and observed the onset of the dog’s diabetes. The next day, Banting and Best, on their own, operated on two more dogs. Both died, one due to an overdose of anaesthetic; the other, from bleeding. Two days later, Banting and Best operated on a third dog. This dog survived the surgery, but it died on May 21st. By then, the first dog they had operated on had also died. 

Fortunately, the next operation, on Dog #387, proved to be successful. Best was able to start a series of tests, followed on May 28th by removal of the remaining segment of the dog’s pancreas. As expected, the animal developed diabetic symptoms: elevated blood sugar levels as well as sugar in the urine. Although Dog #387 did die on June 1st — partly from diabetes, but also an abdominal infection — their first completed experimental work went more or less according to plan. 

The next phase of the research was more delicate and difficult surgically. As per Banting’s idea, it focused on ligating, or tying off, the ducts of the pancreas, and then leaving the organ to degenerate in the dog over the next several weeks. The first dog to have its pancreatic duct ligated, however, died three days after the procedure. The second dog recovered, but Banting was unsure if he had actually tied off the duct. A third ligated dog survived for two days before succumbing to a general infection. 

After the first two weeks of work, seven of the ten dogs they operated on had died. Banting and Best were very frustrated and also concerned about the rate at which they were going through the university’s supply of experimental dogs. Banting was forced to buy some dogs on the street and lead them back to the lab with his tie. There was a vocal anti-vivisectionist community in Toronto, whose members opposed to animals being used in medical research. Macleod was concerned that Banting and Best avoid anything to suggest that dog-napping was going on to supply the university’s animal labs. 

By mid-June, after four weeks of work, things seemed to be going well. Two of the dogs that had had their pancreases removed were healing, and seven of the dogs that had had the duct ligation procedures were doing well. Now Banting and Best had to wait a few weeks before they would be ready to proceed with the third and most critical part of their experimental work, preparing their first pancreatic extract to test on the diabetic dogs. They needed to wait for the ligated pancreas to degenerate sufficiently in each of the duct-ligated dogs before removal; it was critical that there was no external secretion in the degenerated pancreatic tissue. 

In the meantime, Macleod left for a vacation in Scotland. In his parting instructions to Banting and Best, he suggested they contact Dr. J. Bertram Collip should they need help or advice. Collip was a biochemist from the University of Alberta on a sabbatical at the University of Toronto (although he would be on summer vacation in Massachusetts). Macleod had introduced Collip to Banting and Best earlier. 

Best was also leaving the city for a couple of weeks, for militia duty and then to spend some time with his fiancé, Margaret Mahon. Banting was left on his own to operate alone to do another pancreatectomy. In that case, the dog died from uncontrolled bleeding. Banting also had difficultly doing the blood and urine tests. 

Banting expressed his frustrations to Best when he returned. As Banting later recalled, “I told him that if he was going to work with me that he would have to show some interest, that his work was totally unsatisfactory, that he lacked accuracy and was too sloppy, and I ended up telling him that before doing another single thing he must throw down the sink every solution that had been using, wash every bit of glassware and make up new solutions that were truly ‘normal’.” Best, however, took the criticism in stride. According to Banting, “when I finished thus setting him out he gazed fiercely at me for some moments in silence — he looked very defiant — his fist opened and closed — he was very vexed.” Banting wasn’t sure if Best was about to fight him. “Suddenly he turned on his heel, went upstairs and I heard rough usage of glassware for some time.” Best worked all night and then left in the morning. Banting inspected and found everything spic and span. “We understood each other much better after this encounter.” Best decided to stick with the project rather than pass it over as originally planned to Clarke Noble, who would have to learn everything from scratch.

Banting and Best’s frustrations were exacerbated by the oppressive June-July heat and the less-than-sterile conditions of the animal operating room, which roasted under the black tar roof of the Medical Building. Fortunately, the next stage of their work would be undertaken down two flights of stairs, in Room 221 — a small anteroom with bench space and equipment situated next to one of the main physiology labs. For much of the summer, the resident of the main lab, Dr. E. Fidlar, who was busy doing intricate experiments on the respiration of frogs, provided some company and advice to Banting and Best. Fidlar held a Fellowship in the Department of Physiology paid by the Research Fund of the President of the University.

In early July, Banting and Best were ready to check on the degree of pancreatic degeneration in the seven dogs that had undergone the duct ligation procedure. But when Banting opened up the first of the dogs, he was alarmed to discover that the pancreas looked quite normal. Something had gone drastically wrong. He then opened up all of the other ligated dogs. He found that the ligation held in only two, causing the pancreas to degenerate. Banting had originally used catgut for the ligatures, which had clearly loosened. Using silk ligatures, Banting had to carefully re-ligate the pancreatic ducts of five of the dogs. Adding to the frustration, two of the five dogs died within a day of the operations. Another two that had had their pancreases removed died from infections complicated by the hot weather. To Banting and Best the week was a clear disaster, leaving the whole research project not far from total failure. They decided to take a long weekend off to rest and re-group.

For the balance of what was a very hot July, Banting and Best took a slower pace, focusing first on removing the pancreases of two more dogs and finally putting all their work to the test. 

On July 30th, Banting removed the clearly degenerated pancreas from Dog #391 and he and Best proceeded to prepare their first pancreatic extract. Macleod had left detailed instructions. They were to start by slicing the pancreas and putting the pieces in a chilled lab mortar that contained ice-cold Ringer’s solution (a mix of salts in water commonly used to preserve tissues). The mortar was then placed in a freezing brine solution until the contents partly froze. From there, they ground up the pancreas pieces with sand and a pestle. This material was then filtered through cheesecloth and blotting paper, to remove solid particles. Finally, the pinkish filtrate was warmed to body temperature, and prepared for injection. 

On that same day, Dog #410 was the first to receive an injection of the pancreatic extract. After being given four cubic centimetres (cc) of the extract, the diabetic dog’s blood sugar percentage level fell from .20 to .12 within an hour. Based on tests of thirty non-diabetic dogs Banting and Best worked with, the average blood sugar percentage level was .090. They gave Dog #410 another injection, but its blood sugar measurement barely moved. After a third injection, the blood sugar level rose. The dog was given some sugar in water and then hourly injections of extract, but with no apparent effect. The next morning, they found the dog in a coma, and it soon died. Nevertheless, the results of this first extract test were encouraging, as it seemed to have a marked effect. 

On August 1st, Dog #406 was in a coma and on the brink of death when Banting administered 8 cc of the extract. Its blood sugar level had been .50, but after an hour fell to .42, and the dog was up and walking around. Its blood sugar fell further to .30, but the dog then fell back into a coma and died. Still, Banting and Best felt it had been quite impressive to watch the dog come out of a coma, stand and walk. Three days later, Dog #408 received an injection of 5 cc, reducing its blood sugar from .26 to .16 in 35 minutes. There was a similar result with a later injection, and this time the dog remained in good condition. 

With the extract working for a diabetic dog in good condition, Banting and Best on August 4th referred to their pancreatic extract as “Isletin” for the first time. They were also ready to conduct a series of more varied experiments to further confirm the extract’s anti-diabetic effects. After successfully administering hourly injections, Banting and Best then tried administering a much larger dose, the results of which were alarming. Dog #408 suddenly became lifeless and appeared to be dying. They tried reviving the dog and while it improved slightly, it soon died. The cause of death seemed to have been a widespread infection. Despite the abrupt end of Dog #408, Banting and Best had learned much about “Isletin” and its anti-diabetic properties and were eager to send a report to Macleod.

In his August 9th letter to Macleod, Banting was very excited to report that the extract “invariably” caused a reduction in blood sugar. But he also had plenty of questions and was very anxious to continue the work in a better equipped lab. In particular, he and Best needed more help looking after the animals, and they needed better operating facilities. 

Banting planned to work at a slower pace while awaiting a reply from Macleod. Yet he was confident enough in the progress and promise of the research to decide, as he informed Macleod, to wind up his affairs in London and get them off his mind. It was a very difficult summer for Banting personally and financially, living like a student with very little money and less encouragement, including from Macleod. As Banting confessed to his cousin, “Worst of all, no one took me seriously.” Yet, despite the lack of any assurance of a paying job at the university and unsure of his future in Toronto, Banting was still prepared to burn his last bridges in London before knowing how Macleod felt about the work.

While waiting for a reply from Macleod, on August 11th, Banting and Best began another round of experiments, working around the clock for several days. The goal was to remove the pancreases of two more dogs, give “Isletin” to one of them (Dog #92) and compare its effects with Dog #409, which would not receive the extract so as to act as an experimental control. After an initial slow response to the extract, Dog #92’s diabetes remained well controlled over the next 20 days, while the condition of Dog #409 steadily declined, and it soon died. Meanwhile, Dog #92 was given an overdose of the extract, which, as expected, brought its blood sugar level to a below normal level. Indeed, Dog #92, a yellow collie, became something of a pet in the laboratory. As is clear from Banting and Best’s notebooks, and their later accounts, it was an unforgettable time for the pair: intense, productive, exciting, and a period of close bonding between them. 

With Dog #92 frisky and doing well, Banting and Best, on August 17th, decided to proceed with some different experiments. One involved removing the whole pancreas from a dog and preparing an extract from it, rather than starting with a degenerated pancreas. When they gave Dog #92 injections of this type of extract, it seemed to have a similar effect, the dog’s chart showing blood sugar reduced to the levels achieved with the extract prepared from a degenerated pancreas. However, Banting and Best said little of this result in their notes and minimized it later in their first published paper. They remained focused on the hypothesis that the external secretion had to be removed, but perhaps there was a quicker way than waiting weeks for the duct ligations to cause degeneration. 

Banting and Best next tried an alternative to the duct ligation technique. They stimulated the pancreas with a hormone known as secretin, which is produced in the duodenum, i.e., the top section of the small intestine. Secretin normally stimulates the pancreas to produce its external secretion. They speculated that if the stimulation process could be increased until the pancreas produced no more external secretion, the pancreas then could be removed, and the internal secretion extracted. 

However, it was complicated to first obtain the crude secretin and to then slowly inject it into the pancreas over a period of four hours, until the production of pancreatic juice stopped. But Banting wanted to try the surgical procedure and soon he and Best had an extract to test on Dog #92. When it received the first injection on that Saturday night, it was quite sick. But by Sunday morning, when Banting and Best arrived back to the lab, Dog #92 excitedly jumped out of its cage and ran around the lab. This was a profound moment for Banting and indeed he later described it as one of the greatest days of his life.

From August 22nd to the end of the month, Banting and Best conducted some further experiments involving Dog #92, including preparing an extract from the pancreas of a cat using the secretin stimulation procedure. That extract, however, sent the dog into shock, bringing a quick end to further experiments. Dog #92 survived and lingered on for another nine days, its blood sugar slowly rising and condition worsening until finally dying on August 31st. “I have seen patients die and I have never shed a tear,” Banting later wrote. “[B]ut when that dog died, I wanted to be alone for the tears would fall despite anything I could do.”

It had been a summer of intense highs and lows. In early September, Banting finally severed the London connection, returning with one of his brothers to sell his house and furniture. After sleeping on the bare floor of an empty house, early the next morning, as Banting later wrote, “we took a last look at the place of my hours of misery — and yet it was there that I obtained the idea that was to alter every plan I had ever made, the idea which was to change my future and possibly the future of others.”

Shortly after Banting retuned to Toronto, Macleod’s letter finally arrived. Their research had progressed so much since he wrote to Macleod on August 8th. Macleod was certainly pleased with their progress, but also advised caution in being overconfident with their results. There had to be “no possibility of mistake,” he emphasized. “You know that if you can prove to the satisfaction of everyone that such extracts really have the power to reduce blood sugar in pancreatic diabetes, you will have achieved a very great deal.” But, as he added, “It’s very easy often in science to satisfy one’s own self about some point but it’s very hard to build up a stronghold of proof that others cannot pull down.”

By the time Macleod returned to Toronto, Banting’s excitement with the progress of the research had been tempered by his frustrations at not securing a formal position at U of T, and Macleod seemed hesitant to provide one in the physiology department. However, Banting had developed a relationship with Dr. Velyien Henderson, the professor of pharmacology, who was willing to look into a position for Banting in his department. But when Banting and Best finally met with Macleod again, things got testy. Banting demanded that certain conditions had to be met to improve the research and working conditions before he would be willing to continue with the work. He needed a salary, a room to work in, someone to look after the dogs, and repairs to the floor of the operating room. Banting threatened to leave and continue his research elsewhere. Although Macleod was dubious about whether Banting would find another place to conduct the research, he soon relented and promised to do what he could. 

Banting actually had other options. In addition to Henderson’s support, he had found an important ally in Dr. John G. FitzGerald, director of Connaught Antitoxin Laboratories, originally established as the Antitoxin Laboratory in 1914 as a public-service-based part of the U of T Medical School’s Department of Hygiene. Connaught’s mission was to prepare essential public health biological products, such as diphtheria antitoxin and rabies vaccine. Headquartered in the basement of the Medical Building, Connaught had grown significantly during the First World War in size and reputation. Through the summer months, Banting had met FitzGerald from time to time and described the results of the experiments. He had also shared his frustrations with FitzGerald, who told Banting not to leave Toronto without consulting him first.

By October 1st, Henderson had come through with a special lecturer position for Banting in the Pharmacology Department at a salary of $250 per month, a reasonable amount. Macleod had found a room large enough for two dog cages and a laboratory desk, and also arranged for retroactive pay for Banting ($150) and Best ($170). Indeed, Macleod had been quite cordial and helpful following their tense exchange. As Banting later noted, “I thought that perhaps I had judged him too harshly.” All seemed settled and the pancreatic extract experiments could go forward once again. However, some key questions remained: in which direction should the research go, and in whose hands?