The general measures of hygiene directed against infectious diseases play a part in prolonging the lives of old people, but, in addition to the microbes which invade the body from outside, there is a rich source of harm in the microbes which inhabit the body. The most important of these belong to the intestinal flora, which is abundant and varied. The intestinal microbes are most numerous in the large intestine. This organ, which is useful to mammals the food of which consists of rough bulky vegetable matter, and which require a large reservoir for the waste of the process of digestion, is certainly useless in the case of man.[119] In the “Nature of Man” I have dealt with this question at length, as it was an important example of what I regard as the disharmonies of the human constitution. A case upon which I have always laid great stress is that of a woman who lived for thirty-seven years, although her large intestine was atrophied and inactive, as this seems to be a remarkable proof of the uselessness of the organ in the human body. The small size or complete absence of the large intestine in many vertebrates confirms my conclusion. None the less, some of my critics think that my argument is incomplete. To strengthen it, I may call their attention to a medical observation which is as valuable as if it had been an experiment. It relates to a woman, sixty-two years old, a patient of Prof. Kocher at Berne. She had been suffering from a strangulated hernia associated with gangrene of part of the intestine, and had to be operated upon suddenly. The gangrenous portion of the ileum having been removed, the healthy part was implanted in the skin so as to form an artificial aperture through which waste matter from the food passed to the exterior without traversing the large intestine. Although the patient was old and seriously ill, the operation, performed by M. Tavel, was quite successful. Six months later, in a new operation, the small intestine was rejoined to the large intestine so that the fæces were again able to pass to the exterior by the natural channel. In this case, then, the large intestine was thrown out of use for half a year, not only without injury to the general health, but with the result that the patient was completely cured and gained in weight. MM. Macfadyen, Nencki, and Mde. Sieber[120] studied the digestive processes in the small intestine and the nutritive metabolism, and determined that these were active and healthy, the absence of intestinal putrefaction, that evil of the constitution, being specially favourable. [Illustration: FIG. 19.—Diagram of the lower bowel in a female patient. _A.C.N._, Artificial anus: _A.S._, Insertion of the ileum to the colon. (After M. Mauclaire.)] [Illustration: FIG. 20.—Diagram of the lower bowel, after a third operation, on the case in Fig. 19. (After M. Mauclaire.)]