With respect to the poisons employed by _Tophana_, the Locusta of modern days, and her infamous successors, there is less doubt; _Arsenic_, _Corrosive Sublimate_, _Sugar of Lead_, and _Antimony_,[130] were amongst the most powerful of their instruments of torture and death. According to the declaration of the Emperor _Charles_ VII to his physician _Garelli_, the _Aqua Toffania_ was a solution of arsenic in _Aqua Cymbalariæ_.[131] Dr. _Hahneman_ considered its basis to have been an arsenical salt. Others have, with little probability, regarded Opium and Cantharides as the active ingredients. _Franck_,[132] speaking of the _Aqua Toffania_, agrees with _Gmelin_,[133] that it is no other than a solution of arsenic. The _Pulvis Successionis_, another instrument of death, whose title announces the diabolical intention with which it was administered, has been supposed to have been a preparation of lead; while others have considered it to have consisted of diamond dust, and to have acted mechanically. Having thus noticed a few of the more remarkable and interesting features in the literary history of Toxicology, we shall proceed to consider the subject of Poisons, in relation to their operation. A Poison, (_Toxicum_, _Venenum_, _Virus_), has been very correctly defined by _Gmelin_ to be a substance which when administered internally, or applied externally, in a small dose, impairs the health, or destroys life. This definition is adopted by _Mead_, _Sproegel_, _Plenck_, and _Tortosa_, and is to be preferred to every other,[134] not only for its simplicity, but for its independence of any theory relative to the _modus operandi_ of such agents. But it will be seen that, by accepting this definition, we are necessarily led to admit the fact, that poisoning may be acute, or chronic, that is to say, that it may at once destroy life, or produce a disease which can be protracted to any indefinite period. After the erroneous and vague notions which have been entertained upon the subject of “_Slow poisons_,” it is highly essential that the latitude of our belief should be accurately ascertained, and the precise meaning of our terms defined. OF SLOW, CONSECUTIVE,[135] AND ACCUMULATIVE POISONING.