These Vermifuges, or Anthelmintics, are employed for a strictly local purpose—that of killing and expelling intestinal worms. Any powerful Cathartic may be used to expel them. But such an agent should generally be conjoined with a medicine that tends directly to kill the parasite; for after that it will be more easily dislodged. For this purpose the root of Male Fern, Kousso, and the bark of the root of Pomegranate, have been used with advantage in the case of tape-worm. Ascarides are situated low down in the intestine, and may be dislodged by the use of an enema, as of Salt.
Turpentine is often very efficacious in cases of this kind, being at once a poison to the worms and a powerful irritant cathartic.
I have already alluded to Nitrate of Bismuth, as seeming to be an astringent to the mucous surface of the intestine, although apparently incapable of absorption. It has been used with advantage in diarrhœa, and is highly recommended by Dr. Theophilus Thompson in the diarrhœa of Phthisis.
But all other astringents are absorbed; and when they act on the mucous glands of the intestines, it is probably from the blood.
It has been supposed by M. Poisseuille and others that the action of Opium in confining the bowels is to be attributed to a power of checking the process of endosmosis, said to be possessed by a solution of Morphia. I shall afterwards state my reasons for discrediting this explanation. (Vide Chap. IV., Art. Opium.)
Thus we have concluded the list of substances which seem to act locally on the mucous surface, without passing into the blood.
Having previously endeavoured to explain the various modes in which medicines are absorbed and pass into the blood, and having now defined the action of some few before absorption, the greater part of our investigation remains still to be accomplished. The actions of medicines in the blood, and their various and complicated operations in the cure of diseases, have to be traced out, and, if possible, accounted for.
The remaining six Propositions concern the behaviour of medicines after their passage into the blood. The first two of them are comparatively unimportant. The Fifth is merely an extension of the First Proposition,—in which the same rule is applied to the blood which was there proved of a surface,—and indeed follows in part from the latter. The Sixth Proposition defines three kinds of changes which certain medicines are liable to undergo during their stay in the system.