The explanation of these facts appears to be simply this: there is a want of absorption of the venomous substance through the gastro-intestinal mucous membrane. This can be shown by the following experiment:—Take the fresh gastric mucous membrane of a dog or rabbit, recently killed; adapt it to an endosmometer in such a manner that the mucous surface remains outwards; then plunge the endosmometer containing sweetened water into a watery solution of woorara, and we shall find, after two or three hours, that the endosmosis will be complete. The level will have risen in the endosmometer, and yet the liquid contained in it will shew no trace of the poison, as can be proved by inoculating other animals with it.
If the experiment were to last longer, the endosmose of the poison might take place, but we should then find that the epithelium which covers its surface, had become changed, and had permitted the imbibition and endosmosis of the poisonous principle. This is so true, that if a partially decomposed membrane should be used instead of a fresh one, the endosmose of the poisonous principle takes place immediately. On the living animal, we can establish this property of the intestinal mucous membrane, and can demonstrate that amongst substances perfectly soluble in appearance there are some which when lodged on the surface of the intestinal membrane, may remain there without being absorbed, or without affecting the system. The active principle of woorara is of this kind. {81}
It was necessary to ascertain whether other mucous membranes, besides those of the digestive organs, were possessed of this same property with regard to woorara. We have tried it successively on those of the bladder, the nasal fossæ and the eyes, and in all we have found an equal resistance to the absorption of the poisonous principle. An injection of this poison into the bladder of a dog, was retained six or eight hours, with no bad effects; but the urine voided after that time had all the poisonous properties of woorara.
One mucous membrane alone offers a remarkable exception; it is the pulmonary. This acts, in regard to the absorption of woorara, precisely like the sub-cutaneous cellular tissue; and on the introduction of some drops of the poisonous solution into the air passages, when every precaution is taken, death takes place as rapidly as when the skin has been punctured.
We readily perceive that this membrane, destined solely for the passage of the air to accomplish the phenomena of respiration, possesses a peculiar structure, and is unprovided with that protecting mucous which lubricates the other membranes communicating with the exterior. This similarity between the pulmonary mucous membrane and cellular tissue, supports the ideas which M. Majendie, long ago, promulgated on the structure of the lungs.
We shall not expatiate, at present, on the remarkable difference in the absorbent properties of the various mucous membranes of the body. We shall have occasion again to revert to the subject, and shall only state that this fact, in relation to the absorption of woorara, is not isolated, and that in the intestines, for example, many active principles, although soluble, cannot be absorbed, and are consequently forced to act locally, or as if shut up in a closed vessel.
For the present we will content ourselves with these conclusions:
1st. That woorara acts upon animals in the same manner as venom.
2nd. That its harmlessness, when injected into the intestinal {82} canal, cannot be explained by any change which the poisonous principle undergoes, but rather by a special property of the gastro-intestinal mucous membrane which resists its absorption.—Journal de Pharmacie et Chimie.