In spite of the disorganisation of his whole life, Metchnikoff had succeeded in resuming his work to a certain extent. He took advantage of an opportunity to observe an old dog who was suffering from diabetes, and hastened to examine his organs as soon as he died, whilst they were still fresh. He had for some time supposed that diabetes might be an infectious disease; yet he was unable to discover any specific microbe either in the humors or in the organs of the dog. But he succeeded in provoking symptoms of the disease (traces of sugar in the urine) in a healthy dog, by inoculating him with the pancreatic gland of the diabetic dog. He was much encouraged by this result, and would have liked to continue his researches, but was unable to do so because of the general disorganisation and the impossibility of obtaining animals for experiments. He had to content himself with continuing his memoir on infantile cholera and his observations on the silk-worm moth. As he was almost altogether precluded from laboratory work, he began to write a study on "The Founders of Modern Medicine," in order to demonstrate, by concrete examples, the importance of positive science in its application to life. This is what he said in his preface to the book: These pages were written under special circumstances. If not in the actual hearing of guns, it was in expectation of it that I had to spend several weeks in my Paris laboratory, now under war conditions. These meant an almost complete cessation of any scientific activity in our Institute. For fear of a lack of food, the animals used for our experiments had been killed, which deprived us of the possibility of proceeding with our researches. The stables of the Institute were filled with cows who provided milk for the hospitals and children's homes. The greater number of our young collaborators, assistants, or laboratory attendants were mobilised, and only the female employees and old men remained. One of the latter, I found myself in the impossibility of pursuing my investigations and in possession of much leisure. I made use of it to write this book in the hope that it might be helpful. It is not intended for physicians, for they know all that is expounded in it, but for young men who are seeking a scope for their activities.