Judging from the prevalent notions on the subject, from the universal reference of all kinds of bad health to derangement of the stomach and bowels as their source, and from the scarcely less universal use of purgatives as remedial agents, one would be apt to suppose that, to ensure health and long life, nothing more was required than to procure, no matter by what means, an intestinal evacuation regularly every day; and the inference would, to a certain extent, be confirmed by the acknowledged extensive utility of laxative medicines. The real state of the case, however, is not quite so simple; and as it is of importance that it should be understood, I shall attempt to explain it as clearly as I can. We have seen that inactivity of the intestinal canal may arise from the use of too concentrated aliment, and from excess in the other excretions. In the great majority of cases, however, the cause is very different. In general, the diet is sufficiently varied and abundant, and the balance of functions sufficiently equal to leave a considerable quantity of alimentary residue and effete matter to be thrown out by the bowels; and if it is not regularly expelled, some obstacle of a different kind must exist, which, in the first place, ought to be removed, before we can expect to succeed in restoring the natural action. To learn what that obstacle is, let us turn our attention for a moment to the natural means by which the intestinal evacuations are effected. The progress of the intestinal contents along their canal depends, first, on their affording the necessary stimulus to excite the contraction of the muscular coat; secondly, on the assistance derived from the free action of the abdominal and respiratory muscles, not only during respiration, but during every kind of bodily exercise; and, thirdly, on the inner surface of the intestine being duly lubricated with the mucous secretion. If any or all of these conditions be unfulfilled, the inevitable result will be morbid sluggishness of the intestinal action, and the various consequences dependent on it; and hence, when the evil exists, the first point to be determined is the nature of the cause by which it is produced.