Thus, from these four considerations, we are strictly justified in concluding that a medicine must pass from the stomach into the blood before its action can be manifested. This action cannot then be conducted from the surface of the stomach through the agency of the nerves. Some experiments made by Dr. Garrod and others on the action of animal charcoal as an antidote, furnish again an additional confirmation of this fact. He finds that if a sufficient quantity of this absorbing agent be introduced into the stomach before time has been allowed for the passage of a medicine through the mucous membrane, then even such powerful nerve-medicines as Morphia and Strychnia, in very large doses, are prevented from taking effect. Yet before the contact of the charcoal they would have had time to act through the nerves, had they been capable of any such action. In the fifth Proposition the rule here laid down will have to be further extended. It will be shown that medicines, having already passed into the blood, must travel along in it so far as to reach the part of the system on which they act. Before concluding this question, a few remarks must be made on a subject which will be again referred to in the discussion of the Fourth Proposition. The proper and peculiar action of a medicine, by which I mean that action on the system which is immediately recognised as distinct from that of any other agent, cannot be exerted on distant parts from the stomach-surface, but requires the passage of the medicine into the circulation. But can any other action on distant parts be produced by the remedy while in the stomach? This is a different question, and must be answered in the affirmative. Suppose a Cantharides plaster be applied to the surface of the chest in a case of Pericarditis, so as to redden or blister the skin, absorption of the fluid in the pericardium may follow this application. But any other irritant would have done this. It is not the proper or peculiar action of Cantharides, but an operation of the nervous system which follows the local change. Such agents are said to act by _Counter-irritation_ or _Revulsion_, because it appears that, as a consequence of their action, the attention of the nervous system may be drawn off from a morbid process going on at some other part of the body. But it is only a consequence, and not a direct operation. Such an effect is no more the action of Cantharides than the healthy functions following recovery from sickness can be ascribed to the remedy which has cured the latter.