“Disease is only an episode!” he wrote. “It is not enough to cure (he had discovered no cures) ... it is necessary to find out what the destiny of man is, and why he must grow old and die when his desire to live is strongest.” Then Metchnikoff abandoned work on his dead phagocytes and set out to found fantastic sciences to explain man’s destiny, and to avoid it. To one of these, the science of old age, he gave the sonorous name “Gerontology,” and he gave the name “Thanatology” to the science of death. What awful sciences they were; the ideas were optimistic; the observations he made in them were so inaccurate that old Leeuwenhoek would have turned over in his grave had he known about them; the experiments Metchnikoff made, to support these sciences, would have caused Pasteur to foam with indignation that he had ever welcomed this outlandish Russian to his laboratory. And yet--and yet--the way really to prevent one of the most hideous microbic diseases came out of them.... [Illustration: ÉLIE METCHNIKOFF] Metchnikoff dreaded the idea of dying but knew that he and everybody else would have to--so he set out to devise a hope (there was not one particle of science in this) for an easy death. Somewhere in his vast hungry readings, he had run across the report of two old ladies who had become so old that they felt no more desire for life--they wanted to die, just as all of us want to go to sleep at the end of a hard day’s work. “Ha!” cried Metchnikoff, “that shows that there is an instinct for death just as there is an instinct for sleep! The thing to do is to find a way to live long enough in good health until we shall really crave to die!” Then he set out on a thorough search for more of such lucky old ladies, he visited old ladies’ homes, he rushed about questioning old crones, with their teeth out, who were too deaf to hear him. He went all the way from Paris to Rouen to interview (on the strength of a newspaper rumor) a dame reported to be a hundred and six. But, alas, all of the oldsters he talked to were strong for life, he never found any one like the two legendary old ladies. Just the same he cried: “There is a death instinct!” Contrary facts never worried him. He studied old age in animals; and people were always sending him gray-haired dogs and dilapidated ancient cats; he published a solemn research on why a superannuated parrot lived to be seventy. He owned an ancient he-turtle, who lived in his garden, and Metchnikoff was overjoyed when this venerable beast--at the great age of 86--mated with two lady turtles and became the father of broods of little turtles. He dreaded the passing of the delights of love, and exclaimed, remembering his turtle: “Senility is not so profoundly seated as we suppose!”