Certain medicines, which have been called _sheathing_, have been recommended to be taken by the mouth. Of this kind are mucilage, oil, and wax. I have made trial of mucilage, such as starch, without any sensible effect, probably because it loses its qualities by the powers of digestion before it reaches the part upon which it is intended to act. With regard to oil, I have hardly enough of experience of my own to decide; but some of the surgeons of the fleet informed me that they found advantage from combining it with the purgatives. I was discouraged from using it by finding that it was apt, in the West Indies, to become rancid on the stomach, and, for this reason, I seldom, in any case, employed the castor oil, which, though produced in that climate, seems to answer better as a medicine in Europe. But since my return to England I have used, with great benefit, at St. Thomas’s hospital, a medicine, composed of tincture of rhubarb and oil, in old dysenteries, attended with discharges of blood. I took the hint of this from finding it of great service in deep-seated piles, as recommended by Dr. Griffith[115]. It is necessary to combine something purgative with the oil, otherwise it might be altered by digestion, or absorbed, or might become rancid by too long retention in the first passages. Wax is a body not changeable by digestion, and seems therefore well suited for the purpose of sheathing the bowels; and I have found advantage from the preparation of it recommended by Sir John Pringle[116], on the authority of Dr. Huck. I have also seen some advantage in old fluxes, in St. Thomas’s hospital, from the use of spermaceti, given with an equal quantity of conserve of roses and half as much absorbent powder, agreeably to a form in use at that hospital. The climate has a great influence in preventing these ulcers from healing, upon the same principle that it prevents the cure of external sores and wounds, so that there are cases that admit of no cure but from a change of climate. I have seen in some cases of old dysentery, small, round, ill-conditioned ulcers break out on the surface of the body, which seemed to proceed from the same general habit that produced those of the intestines. There was something peculiar in the appearance of those external sores, being like small round pits, as if a part of the skin had been removed by caustic, and with little or no discharge. In a case of this kind, which proved fatal, I found the whole surface of the great intestines beset with small ulcers, not unlike those on the skin.