Formerly all acute diseases were supposed to depend on morbific matter taken into the body, and absorbed by the blood: the cure was thought to be accomplished by the expulsion of this morbific matter from the body by sweat, or some of the other natural evacuations. The doctrine was attended by many difficulties, and in many cases did not admit of a satisfactory explanation. It was therefore laid aside, and the debility or excitement of the nervous system arose in its place. But this new system admitting of _miasmata_ and _contagion_, it was plain that morbific matter still kept its ground. With a view, it would seem, to render the nervous theory more complete, it has been found necessary to deny the doctrine of contagion and infection entirely. This has been done, wherever there was a possibility; but the phenomena of the small-pox and measles, as well as those arising from poisons, still militated strongly in favour of morbific matter. To avoid the force of arguments drawn from these sources, the doctrine of absorption was denied, and contagions of all kinds were said to act immediately upon the nervous system without affecting the blood or other fluids. At last the matter seemed to be decided by the experiments of the Abbe Fontana on poisons. He found that some proved fatal by being mixed with the blood, others by being applied to the nerves, and others by being taken into the stomach. Even this did not give satisfaction. It was contended that the effects of poisonous bites were too quick to be accounted for on the principle of absorption; that, after the most violent symptoms had commenced, they might be removed by cutting out the part affected; and consequently that, instead of any absorption by the blood, we were only to believe that the nervous system was irritated.