place in too short a time to be considered as the result of inflammation; and in the next place, in whatever manner the poison is applied, whether _externally_ to a wound, or _internally_ to the membrane of the stomach, the inflammation is confined to the stomach and intestines; and, indeed, it is commonly more violent, and even more immediate, when applied to a wound, than when internally administered; and it also precedes any inflammation of the wound. This important fact was proved by an experiment made by Mr. Hunter and Sir Everard Home, and subsequently by the repeated investigations of Mr. Brodie. It has been just stated that after a poison has found its way into the circulation, it expends its virulence upon some particular organs. In some cases this is much more striking than in others. The preparations of _Baryta_, and of _Tartarized Antimony_, attack the heart, and occasion death by syncope. _Arsenic_ is less definite in its action, it influences both the brain and the heart, but with different degrees of force in different cases, so that it is often difficult to ascertain which of these organs is the first to fail in its functions. _Hydro-cyanic Acid_ is absorbed, and destroys life by its action upon the nervous system, whose energies it would seem to extinguish without any ostensible injury to the respiration and circulation; for in all those animals which were killed by it in the experiments of _Orfila_, _Brodie_, and others, the heart was found acting regularly, and circulating dark-coloured blood; and in some cases, this phenomenon was visible for many minutes after the animal was in other respects apparently dead. Some substances would seem to direct their powers to various parts of the alimentary canal; and the appearance so produced might be mistaken for the effects of the local action of the poison, had they not been clearly proved by experiment to have arisen from an application addressed through the medium of the circulation; thus is inflammation of the _primæ viæ_ induced by the contact of Arsenic with an external surface of the body! The _Third Class_ of my arrangement includes those poisons which enter the circulation, and, through that medium, expend their influence upon the spinal marrow, without _directly_ involving the functions of the brain. _M. Majendie_, in the year 1809, submitted to the first class of the French Institute a series of experiments which had conducted him to the extraordinary result above stated. He found that an entire class of vegetables (the _bitter Strychnus_) possesses this singular property. The _Fourth Class_ comprehends all those substances which destroy life by a local action upon the alimentary canal, not by any impression upon their nerves, but by simply inducing a fatal lesion in the membranes.